DO NOT JUST QUICKLY SIT OR LIE DOWN ON A MATTRESS, ROLL AROUND ON IT, TWIST, TURN, SIT UP, LIE BACK. Sorry about the all caps, but I can not stress enough how important it is to really try out the mattress first, but actually trying it in every conceivable way before you make a choice. My DD bought a new mattress and insisted I come try it out. It happened to be a pillow top, which is not on your list, but this makes my point for me. She still raves about that silly mattress, but when I lie on it, I can't move, and my back just screams with pain. See if the seller offers a "money back try out period" would be my best suggestion.

No suggestions on mattresses, but I have a suggestion regarding your hip replacement. I had mine in 2005 and my orthopedist suggested putting a bed pillow between my legs when laying on your side. The pillow keeps your hips in neutral position (ankles, knees and hips in straight line) and makes turning over so much easier. Ask your doctor if this would work for you. (I slept with the pillow for about 6 months).

Good luck on your mattress shopping. One thing I do recommend, is a flippable mattress. Most pillow tops can't be flipped. Also, pillow tops can be thicker than non-pillow tops and you will need extra-depth sheets. Regular sheets will pop off on the corners.

I have severe back problems, degenerative disc disease, sciatica, dorsal nerve stims, upper and lower. 9 spinal surgeries, and a mess of other things. Memory foam saved my life. I swear by it. got about 6" of it on my bed. can't live without it.