While I don't have chronic back pain, I do have it occasionally and took that into account when buying my current mattress (which I got like 7 or 8 years ago). I went with the Select Comfort bed. The ability to change the firmness makes all the difference in how my back feels the next morning, sometimes I need firmer support than others.

I'm 6'3" and 205lbs, and the mattress has held up very well. I did spend quite a bit on it (either top of the line or second from when I got it), but I feel that it was well worth it.