Mattress Forum

I am a big guy 6' 4" 215 lbs and have an achy back.  I always thought I should have a firm mattress, but after going and laying around on some, i found I really like something a little softer.  I like some of the temperpedic beds also.

So, I see costco sells some memory foam mattress that get mixed reviews.  I am half temped to try one out and if I dont like it, take it back.  However, none of them come with a foundation.  Should i just find a cheap box spring around town or should i get a specific foundation?  

Any suggestions on what to do about a foundation would be great.