The most comfortable bed I have ever had was a regular mattress with a 4 inch foam topper from either Walmart or Sam's Club.  I don't remember where I bought it.

My husband has back problems and nothing would do him but that we buy a tempurpedic.  They come in two thicknesses.  Don't buy the thickest one if you are short.

I love my tempurpedic pillows and the mattress is OK.  It isn't quite as comfortable as what I mentioned above.  It didn't help my husband's back problem either. 

My husband and I both have a problem with the edges of the tempurpedic.  The edges are weaker and if you sleep close to the edge you feel like you will fall off because it slants. I have to scoot over a foot farther than I did in other beds to avoid the edge.