Hi Steve,
I agree with you and the statement I made was rather broad but had a different context than your example.
There is a noticeable difference between 19 ILD and 24 ILD (or 23 which is not an LI “rating”) even though the difference is relatively small. This is because it represents a larger percentage change. A 4 ILD difference in firmer latex would not represent as great a percentage change and would be more difficult to tell. I also meant that the ILD rating themselves are probably not accurate and all latex has a “range” of ILD across the surface. In a talalay layer … the actual ILD is an average that can vary in different places on the layer by as much as 4 ILD from the softest part to the firmest part and even the “average” ILD is rated to a “standard” it is closest to. In the case of Dunlop … the ILD variances across the surface are even larger than talalay and because of it’s higher sag factor even a lower ILD rated at 25% compression can feel firmer than a higher ILD Talalay where someone sinks into the layer more than 25%.
Dunlop ILD ratings are also often a “guess” and at best are only the midpoint of a range.
My main point though was that you may be surprised that it doesn’t make as much difference in a support layer with wool over it as you may think in the same way that you didn’t notice much difference in the Firm, Extra firm, and the Innersping with the Wool topper over them.
Actually Latex International themselves calls 24 ILD “soft” and anyone that rates their material differently is disagreeing with the actual manufacturer of the latex and creating confusion. The 19 is called “plush” and the 14 is called “super plush”. Some manufacturers use a “standard” top layer even firmer in the range of 28. In addition to this … ILD ratings in latex are different from ILD ratings in polyfoam because latex is “tested” with a 6" core while polyfoam is tested with a 4" core. This would mean that a latex ILD is actually softer than it would seem using a polyfoam ILD rating as a comparison and as you can see by the chart on this PFA page the difference in in the range of 20%. This means that 24 ILD latex tested on a 6" core would be similar to a 19 ILD in polyfoam tested on a 4" core.
Flobeds don’t include ILD information at all but I would imagine that since they use LI talalay that their firmness ratings would be the same as LI just like SleepEz. If it was different from their own supplier then they would be contributing to more ILD confusion which I doubt (but could be wrong). The middle and lower layers would be the same but of course their design concept uses a “standard” convoluted soft layer on top of all their mattresses which is the same for all their models and is closer to mattresses.net design which also used a standard “soft” layer on the top of their standard mattresses and changes the core below this to adjust firmness.
Each person will have a different sensitivity to the ILD differences they can feel and some of this is often because two different layers may not even match the ILD rating they are assigned or think they are testing. For example a 32 ILD LI Talalay may actually be 33.9 and a 36 ILD talalay may be 34.1. ILD is always best thought of as a “range” rather than an exact number and it is not nearly as exact as people seem to think either in “fact” or in the accuracy of people’s perceptions. Unfortunately there is no consistent meaning or standardization to the “soft, medium, firm” terms or their variants in either a particular material or between materials and I doubt that this is coming anytime soon.
All of this though is moot to the point I was making (or trying to make and poorly it seems) which was about finding out how much difference you could feel in the different core layers with wool on top.
Do you have any memory of which you prefer when you were testing them before? The Dunlop is more supportive and denser/firmer so would hold up weight better in an equivalent ILD. Talalay is more 'springy" and in an equivalent ILD would allow for a bit more sinking in. Did you have a preference between the two at Soaring Heart with the wool on top? I iwould go by either your preference of reel based on testing both or on which was more important to you … either “holding up the hips” (Dunlop) or “allowing the shoulders” (Talalay). This is assuming equivalent ILD’s of course because bvoth the holding up and the allowing can be adjusted by changing firmness levels in which case the feel of each would become the most important.
I don’t keep an ongoing record of pricing but I would look through the manufacturer members of the site listed in post #21 here for the latex core. Here in Seattle I would also call the local manufacturers to check their prices for a core you wanted. Post #4 here also includes some DIY sources and some of the polyfoam outlets also sell latex but I don’t have a list of their prices and in my experience they are not in the same price or value range and I doubt would be any better. Other than this … an online search would bring up more options (although mostly toppers rather than cores) and but again I doubt you will find better pricing/value than is listed on the manufacturer’s list for the site.
In terms of foundations … I personally prefer a slatted or grid type foundation for latex because like Soaring Heart I believe they ventilate better and reduce the risk of mold and mildew. There are many others who say that a solid platform foundation is also fine but I am in the “more ventilation is better” camp and perhaps more risk adverse.
There are quite a few posts scattered around the forum with foundation sources from very inexpensive to much more expensive and my thoughts about the different options. Some of the better ones with links to various choices include post #4 here … post #13 here … post #47 here … and post #2 here.
I hope I covered all of your comments and questions 
Phoenix