Memory foam mattress recommendations (bedroom, cost, vent, mattresses)

[War Beagle]

I need to eventually set-up a guest room and the plan is to put my current mattress in there so I can upgrade to a king size mattress for my own bedroom. My current queen is a Tempur-pedic and it is fantastic. That said, I would prefer not to spend several thousand dollars on a mattress again if it is not necessary.

Does anyone have any experience with the less expensive memory foam mattresses? I prefer a firmer memory foam mattress and would like one that is going to last a while.

[wit-nit]

We love our Serta IQ firm memory foam mattress. Cost about $1200.00. It's a lot cooler and more comfortable than the Temperpedic we tried.