Hi jwevans01,
That’s very difficult for me to say because of course “theory at a distance” can never be as accurate as actual testing and knowing specs can only go so far in “predicting” how well a mattress may work for any individual.
I can say though that more conforming can also be more supportive and that while you may be a little deeper in the box top mattress overall, the extra latex will adjust well to any heavier parts because it gets firmer faster than other foams so it can be both more conforming and supportive. Being able to sink in a little deeper with your more “pointy” parts can also result in the gaps in your profile being filled in with a little more firmness which also helps to support them better as well (such as the small of the back).
If you tested the mattress carefully while you are very relaxed and your muscles had “let go” and you were in good alignment and didn’t feel any tension or pain in your back or a tendency to hold up parts of your body … then the odds are very good that it will work well for you.
To re-assure yourself though … it’s always a good idea to ask what their adjustment policy is if it turns out that even the best of testing doesn’t quite get it right. While this is not likely … it’s always good to know for peace of mind.
The Dormeir is without a doubt one of the best choices in mattress protectors available. It is quite thin and stretchy so it has a very good combination of breathability, water resistance, and doesn’t affect the feel of the mattress as much as many other alternatives … particularly wool ones.
Most of the research for the site goes into mattress materials and sources so I don’t have a list of the best buying sources for sheets or bedding as it’s not my area of expertise. There are some very good sources of information about different types of sheets and what to watch out for. This can also be more complex than many would think because misleading or inaccurate labeling is also very common in bedding.
One of the most informative sites about the different types of materials used in sheets and bedding is St. Geneve (which makes the Dormeir mattress pad). http://www.stgeneve.com/quality_defines/bed_linens.htm
A good general overview is here http://www.cuddledown.com/product/articles/buying-guides/how-to-choose-fine-linens.do
Another very helpful article is http://www.canadianliving.com/life/sleep/how_to_pick_the_perfect_bed_sheets.php
and another is here http://www.cuddledown.com/product/how-to-choose-fine-linens.do
A few sources that I’ve gathered in my travels include …
http://www.specialtylinens.com/sheets.htm
http://www.landsend.com/
http://www.sleepbuyersclub.com/bed-sheets.html?show=GO
http://www.egino.com/jersey-knit-sheets-our-product-description.html
http://www.linenplace.com/
http://www.cozytownlinens.com/ Custom pocket sizes from 6" to 25"
http://www.hardtofindsheets.com/index.htm Carries some difficult to find types and sizes of sheets
http://www.bambooki.com/100-percent-bamboo-fiber-unique-sheet-set-by-bedvoyage Split king bamboo sheet sets.
London Linens & Rugs Australia Also makes custom sheets with any pocket depth, size, or shape including split king sheets.
My “vote” would probably go for linen (flax).
Post #7 here has lots more information about sheets and different fibers and fabrics.
And of course … if you (or anyone reading this) come across more … it would be great to add to the list 
Phoenix