A.P.
We were in the same position a few years back! It was such a hard decision to make.
We looked into the "foam" mattresses & then we really thought about it.--We'd be sleeping (and doing other things that you do in bed) on a giant SPONGE. Gross! No thank you.
We opted for the Sleep Number bed & have (for the most part) been pretty happy with it. It does have a few drawbacks (ie: off-gas'd for a while & if you sleep in the middle of the bed (but have 2 air chaimbers) it feels funny) but I like that if one "part" of the bed broke, got damaged, etc... it could be replaced. It also has a 20 yr warranty. We've had it for about 7 yrs or so now & have yet to have any issues with it.
If I were looking now, I'd get an organic mattress, but hopefully we won't need a new one for a very long time!