So, I'm considering buying a PU foam mattress, and thinking of putting one together from FBM or similar. Just came across a foam store in NYC that has a very good reputation--"dixie foam"--and they also have enticing names for their foam beds, i.e. 'dreambed', etc. They have a foam mattress that is 2.8 density, and they offer this 5.5" foam mattress plus a 2" super-soft topper for $760. I can buy it from FBM for about $500. Wondering if foams with the same density would vary much in quality/feel??