Hi Preggo,
I can certainly see that you like “soft” mattresses 
The first thing I should mention is that if you are planning to have a baby or infant sleep on your mattress at times … then I believe you should completely avoid all memory foam. It is not suitable for babies or infants and could be dangerous.
Stearns and Foster has 6.5" of soft polyfoam foam on top. The iComfort Revolution has 5 3/4" of soft polyfoam and memory foam on top. Both of these are a recipe for early foam breakdown and a repeat of your other experiences.
I made a few calls this morning to see what was available around you and I have to say that there is not a lot. You are in a “difficult” area of the country in terms of buying a quality mattress that will last (I looked at what I knew about or could find within about 50 miles or so). Some of the calls I made today and the websites I looked at include these …
http://www.beds4u2.com/products.html Retailer in Lynchburg. They carry a brand called Paramount which is a regional manufacturer which may have some better value. I would make sure thought that they can provide you with the information you will need about the quality/density of all the layers in their Paramount mattresses because they may not be completely transparent about the foam densities of the layers in their mattresses.
http://perfectlatexmattress.com/ or http://sleepessentials.com/ Roanoke, Henrico, VA. They are an independent manufacturer which makes high quality natural latex mattresses. While I realize they are some distance from you … they are really the only ones I think highly of and I believe would give you truly accurate information and not lead you astray. I have talked with him for several hours and he will certainly IMO help you find the type of mattress and type of construction that would be most suitable for you.
ADDED: There is now a more complete list for the larger Lynchburg. Charlottesville, Waynesboro area in post #3 here.
While they may be a little over your budget (King size is $2400) … a similar mattress in mass market outlets (if you could find something similar at all) would likely cost well over $1000 more. They are good quality and reasonable value.
The first step is to find out which version of his mattresses would work the best for both of you. The final step is to make a decision whether to actually purchase that mattress or whether the knowledge you gain can help you find something similar that is a little less … or if that would even be worth considering.
I wish there was more around you that was even worth considering … but unfortunately (to my knowledge) … there isn’t. At least there is one outlet which you can count on to give you accurate and reliable information and who is more interested in finding something that actually is suitable for you and long lasting than they are in just “selling you something” for the sake of the sale itself.
Hope this helps
Phoenix