I've found my mattress!
I stopped by Yankee Mattress Factory today, and was very impressed! They specify the density of the polyfoam used in their mattresses right on the card posted to each mattress, as well as the type of coil. The salesman was knowledgeable about their products (down to the gauge of wire used in the coils) and was able to guide me through the available models in my price range.
I tried three models. I did not take nearly as many notes as I intended, since the choice became quite simple once I had all the facts. All of these are no-flip mattresses.
The first model had offset coils, if I remember correctly. It also had ~3" of 1.8 lb/cu. ft HD polyfoam, which was somehow stitched into the mattress (so it could not be separated or replaced independent of the coils). Very comfortable! I took my time evaluating it on my back and side for ~5/10 mins, and was happy to feel that I would be able to comfortably sleep on my side on this mattress.
The second model was similar (~3" of 1.8 lb/cu. ft HD polyfoam for comfort layer), but it used pocket coils, and the comfort layers could be replaced independent of the coils. HUGE DIFFERENCE in comfort. I could really feel the extra 'give' that the pocket coils supplied; my spine seemed to give a sigh of relief. This model costs $100 more than the first.
The third model was identical to the second model, but it used ~1-3/4" of 1.8 HD polyfoam and ~2" of 1.9 HD polyfoam (if I remember correctly). I did not see much of an advantage over the second model (other than the slightly bolstered durability), considering that it was more expensive. This model costs $100 more than the second.
I ended up purchasing the second model -- a 'Springvale'. I recognize that the HD polyfoam may not be the best choice from a durability standpoint (since the mattress guide recommends using it in combination with a denser polyfoam), but I'm not too worried about it. If the comfort layers sink more than 2", then I can get a replacement under the warranty. I plan to rotate the mattress every 2-3 months. If I am bothered with degradation that is not covered by the warranty, then I can spend some money to replace the layers through Yankee Mattress Factory without replacing the entire bed. They are very up-front about the body impressions being normal and expected, so I know what I am getting into.
I ended up spending a total of $877.58, which covers:
- Queen 'Springvale' mattress + boxspring: $699
- Queen Frame: $79.95
- Tax: $48.68
- Delivery + removal of my old mattress+boxspring: $49.95
Also, since business is a bit slow this week, they will be able to build everything tomorrow and ship it to me on Thursday. Overall, a very good deal.
Due to time constraints, I was unable to visit Fly By Night. I guess those models will remain a mystery.
Thanks for everything, Phoenix! I'll check in sometime later to let you know how the mattress is holding up. Also, I let the salesman know that you directed me to their store; he had never heard of the site. It would be cool to get them as one of your listed partners.