Does anyone know if the sealy mattress they sell at costco are any good? Or are the made from lesser quality? I recently saw a sealy princeton III for $99. It seems firm enough for me, with a little spring... but will it hold up. I believe it was made exclusively for Costco. Does anyone have experience with their mattresses? Does a childs mattress need to be super firm? Also wondering if this mattress will fit in a trundel? gosh so many diecisions. Just wait till we need to pick a college. Yikes