We purchased a new Simmons Beautyrest Recharge mattress set in May 2013, and have been very pleased so far. Ours is called Luxury Firm. It is more firm than a regular pillowtop, but does seem more supportive than some that we had looked at. I believe that that the mattress depth was 14.5 inches.
They carry this Beautyrest mattress line at Macy's if you have one close by to check them out in person. Also, an online source called "Sleep like the dead" has some mattress reviews that may be helpful.
Good luck in your search. It is hard to select something that has to last a long time, and that you don't want to replace again.