Buying a bed can be very frustrating. Do you want to know what's the difference between a $600 set and a $2000 set? It's the support. Beds have weight limits. They don't mark them with weight and the sales person never wants to talk about it. If you don't do it in the right way they lose the sale. So when you are looking, take in your own size and how long you want to own this bed.
The box spring is important for your bed. It acts as a shock absorber so the mattress doesn't have to. Every time you buy a mattress, buy the set. The box spring is a fraction of the cost.
The most important piece of your new mattress will be your bed frame. It's not an add on sale; it's the problem solver. Bed frames more than 10 years old are probably no good. Mattresses are way heavier than they used to be. The first part of a bed that breaks is the frame, then the box spring and lastly the mattress. Get the best frame, which typically costs $120.
Lastly, also when buying a new mattress, go to a mattress store, not Macy's, Sears, or any place like that, but a mattress store. You can buy beds at about 30-45 percent off, except Tempurpedic or icomfort. Once you find the bed you like, tell the sales person I want this bed and yes I'll pay delivery, but I'm paying how ever much. They will say let me see what I can do and will try to will and deal. Just stay nice and polite. Go when they are first open or are about to close. They want the first and last sale.