Thank you, Phoenix, for providing such a wealth of information. Unbelievable site! That said, I thought I would share my purchase decision and what I learned along the way, in case it’s helpful to those researching endlessly as I did. I know this will be long, but am truly hoping that others can benefit and avoid the information overload and subsequent inertia that I experienced 
Background: Like just about everyone else, we needed a new mattress pronto to replace our failing big S-brand coil mattress. Bought a Novaform memory foam at Costco before thinking it through, and I have been miserable ever since. It’s like sleeping on a hard, hot rock. My husband has never been happier or snored less—so, firm is the answer for him! After reading the information here, we thought a natural or organic mattress of higher quality would be more in line with our organic, chemical-free lifestyle than an overpriced, cheap polyfoam traditional mattress (and memory foam is now out of the question). We quickly narrowed it down to either all latex, or a latex over coil hybrid. I actually like coils, and our old mattress served us well for a good decade.
We visited 2 outlets in our area, both within miles of our home: European Sleep Designs (Berkeley Ergonomics retailer) and The Natural Bed Store (many organic/natural brands). Both had knowledgeable, wonderful experts, and we really wanted to purchase from either one, both to support our local economy and receive personalized service. Unfortunately, neither one could offer the “personal value equation” match that we were seeking. I personally do not want to waste anyone’s time and energy “pretend” shopping for a mattress with full intent to buy online, so we knocked out the natural bed store immediately as their promotional all-latex (Omnipedic?) was $4200, and way out of our ideal budget of $2K-$2500k. Every one of their latex beds, including Pure Latex Bliss, was priced way over our budget. I do appreciate that the owner was willing to negotiate lower pricing on multiple mattresses (as we are looking to replace our two young kids’ twin mattresses, as well), but we still could not swing it. I may purchase accessories (covers, pillows, etc.) from this store in the future, however, as I appreciate their attitude and willingness to help us.
ESD, on the other hand, initially offered a better value to us in their latex over coil lines, so we spent 3 long visits attempting to find the right fit for us. While we liked the flexible foundation system a lot, and found their “Baltic” line to be of high quality materials (1100 individually wrapped coils, 2" all natural talalay, organic cover), their ability to customize a mattress for two very different body types was limited (me: 5’8’ 118 lbs, small framed; him: 5’11, 200 lbs, dense framed and broad shouldered). The mattresses that felt great to me were consistently a level “A” in firmness (they don’t share the ILD ratings); the mattresses my husband felt great on were level “D” firmness. Unfortunately, they will not split-construct a level “a” (California King) next to anything other than a level “b”. Likewise, you could get a c/d combination. Given husband’s heavier frame, we would need a level “c” at a minimum, with the firmer spring choice, which did not allow me to sink in far enough and was not ideal in comfort. I experienced pain in between my shoulders on these mattresses, even with a flexible slat adjustment. While a soft talalay topper helped quite a bit, I do not feel that spending an extra $700 on a mattress topper should be necessary to meet both of our needs.
The price on our only workable ESD option (Baltic, level 'c" and “d”), would be: $2800 (mattress plus flexible slat system) + talalay topper $700=$3500. This does not include CA sales tax (8%) PLUS shipping ($85)—which really irritates me, since I live 2 miles from to the store! So, all told, for a mattress that is not fully customizable to our particular needs, we would need to spend $3865. Add to that the reality that if the mattress is not a good fit and must be returned, you must pay a 20% re-stocking fee. I also did not like the fact that they do not offer multiple mattress discounts—or any discounts, even when you mention the Mattress Underground, without whom I would have never even considered (they really should give a discount to your mattress forum members)—unless the second/third mattresses are a full sized or above. While I understand that they feel they offer a good value every day, their shipping and return policies, lack of up front specific information about ILDs/construction, combined with their unwillingness to acknowledge the kudos they receive from online sources such as this forum, turns me off and ultimately lost them a sale. Finally, it takes 3-4 weeks to get the mattress, which would be fine if it were a particularly good value to us, but again, not so much.
While we were there at ESD, I tested their all natural 8" latex model several times and found it a much better match for me. I nearly fell asleep in the store! This lead us to determine that an all-latex model would be best for us, but at $3900 for a 2’ talalay comfort layer plus 6" Dunlop layer and foundation, I knew we could get a better value online. The problem is, again ,that they do not share their ILD ratings (we liked “a” and “b” in the comfort layers on this one), and I know from this site that mimicking a setup is an imperfect science with another manufacturer. Still, it gave us a good starting point.
On to the next narrowed down, online choices, for all-latex based on this site’s information: Custom Sleep Designs, Brooklyn Bedding Co, and Sleep Ez. First, I love CSD, and did not expect such a high level of customer service from simply filling out our profiles online. I have received a totally customized profile, photos, and 2 telephone calls from them in 2 days. Sadly, even with their newer lowered costs, the mattress would be $3500, and is again out of our range. Still a better value, IMO, than European sleep designs, but I can’t swing it. Really feel bad about it, but would highly recommend for those needing very specific configurations. In fact, if the one I just ordered does not work out, I will immediately call CSD.
Brooklyn Bedding Co: Based on Amazon reviews of the company overall, and the reviews on this site, I was all set to order their newer 10", total latex mattress. I liked that the site says Centripur certified, Oeke-Tex (sp?) certified, etc. Chatted online with 2 reps: Mario and Jacob. Interestingly, both had different answers on which type of foundation was necessary—one said no foundation needed (even though I explained that my wood slats were spaced far apart) would be fine, another said 2" slats, and neither was particularly informative on where to find an appropriate foundation to meet the warranty requirements. I Sure wish they would offer a foundation or get it together on what exactly constitutes an “appropriate” foundation, in their company opinion, to meet warranty requirements. Speaking of the warranty—sure is vague, and offered me no assurances. While I realize warranties are generally useless, I do think the manufacturer should be a little less vague. I will also say, as I have not read it before here, that there sales force felt thinly-veiled, high pressured to me. Different answers on the same questions, 5% discounts offered “if you buy today” with discount codes (I did not mention the Mattress Underground), “I’m here for you” assurances, and statements that I would never need foundations, toppers, exchanges, etc. They might make a great mattress, but I was getting the b.s. red flag. Could be wrong, but I think people should be aware.
As for the BB materials, I was willing to go with blended talalay rather than 100% natural or organic, but only upon really digging in did I realize that their bamboo cover has a layer of polyfoam. I think? I was also concerned that their return policy required shipment back at the buyer’s cost. Not interested in that at all, so between the cover and return issue, it was a deal breaker and I moved on to:
Sleep Ez. Again, highly rated and well thought of on this site and others. Although the layer exchange cost is higher than BB, the $99 flat return fee is much better, as is their natural cotton backed by wool cover, IMO. My only concern was that I saw no Oeke-Tex certifications on the website, or anything acknowledging purity standards. After much back and forth between their site and Flobeds, I contacted Sean at Sleep Ez and told him what I needed. He referred me to the Latex Int’l website, explained my options, and came up with a good starting point for a split construction (me: s/m/f; husband m/f/xf). We ordered the natural 10000 with foundation (with 5% discount and 2 free pillows). All told, $1400 less than the ESD, $1100 less than CSD, and $100 more than BB . Yes, it’s somewhat of an apples to oranges comparison, but I am crossing my fingers in hopes that this is the one 
I will update once the bed is here!