We spent a couple of months looking at pretty much every inner spring and most every type of foam mattress. Our ultimate conclusion is that a consumer can't trust the claims of ANY manufacturer and the industry as a whole has branding and model naming strategies that pretty much keep even a determined and savy shopper from even getting close to a smart buying decision so our decision was to buy a new 100% waveless uitra firm extra lumbar supporting watebed mattress and it is, for us, the untimate WOW for comfort, support and deep sleeping.
That said, one of the more comfortable and supportive feeling mattresses (based on 10 minute tests in a store) was the Serta Vera Wang latex mattress. It is a 100% 6 inch latex core on a 2 inch support base with about six other type form layers on top of the latex core.
This seemed to be a mostly latex at a sort of reasonable price which was $1700.00 at the furniture store we tried it out in. Frankly, based on manufacture costs of things like mattresses in our opinion they are ALL way, way, way over priced with a HUGE margin between cost and retail price. That's one reason the waterbed mattress seemed so cost effective @ $300 including shipping and no tax from an online vendor but we have slept on waterbed mattresses for like 22 years so we could be confident that the new models would have enough support along with the firmness we need at our age.
I would not buy an inner spring from ANYBODY - they just don't last and even the manufacturers will say that matresses probably should be replaced in five to seven years tops. If I was going to buy a foam mattress I would buy latex - more comfortable and durable than tempur-pedic and a LOT less expensive.
Best of Luck