Sleep problems

The bed that I sleep in is getting in bad repair. The bed is sagging. After a few years of ware and tare the center of the bed is sagging lower than the bed edging. With the problems with my back and knees I need to get a mattress that holds my back well enough and wont kill my pocket book. I am thinking about using a futon (japanese) mattress with a cheep or ok frame. This should not put me back too much but it still is going to hurt. I can't sleep in bed with my wife because of the schedual I keep. There is a problem with temp control between me and my wife. She is a tropical princess and I am a winter person. If I could go and write a check I would go to my friends store and get what he has called the "Ultimate Sleep Center". That would be a 11" futon and a very pretty sofa/bed frame.