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.