Hi dchuck,
It would be interesting to know how deep your impressions are when you are off the mattress and whether the impressions are deeper than the warranty exclusion (you can measure this by making sure that the mattress is on a completely flat surface so any sagging isn’t coming from under the mattress and putting a straight edge over any impressions and using a ruler or tape measure to measure the actual depth of the impression). In most cases the impressions will be less than the warranty so you may not qualify for warranty coverage anyway if it turns out to be foam softening or “virtual impressions” that are only apparent when you sleep on the mattress.
I can completely understand the “information overload” and I would keep things as simple as possible. When it comes to latex then the main difference in “feel” would be between Talalay vs Dunlop and if you can test both in different firmness levels and end up liking Dunlop better then you could look at the different blends in specific mattresses that you are considering as an additional consideration. I would talk to each manufacturer about their specific mattresses so they can help you with how they would compare to others. In general it’s more effective to 'talk with the experts" than to do all the research it would take to become one yourself.
I’m not sure where you are in Rhode Island (I don’t know your city or zip code) but most of the better options I’m aware of would probably be included in the Boston list in post #2 here or in the Connecticut lists in post #2and #4 here.
Phoenix