Hi dom15,
You can see some of my thoughts about Design Sleep here and here. They carry Berkeley Ergonomics mattresses which are high quality mattresses that use good quality materials and components and don’t have any weak links in their design and would be well worth including in your research. A forum search on designsleep or an exact term site search on design sleep (you can just click both links) will bring up more comments and feedback about them.
Some of the better options or “possibilities” I’m aware of in the Columbus, OH area (subject to the quality/value guidelines here) are listed in post #2 here.
Phoenix