I know a lot of people house adult males in 32qt's, and some that breed in 32qts. Personally, I think a 40ish qt is better for adult males and small females, and that something a litter bigger would be best for the big/gravid females and breeding pairs.

Back or belly heat is lonnnng discussion and pretty controversial. I use belly heat since I really dont any reasons to use back heat...but maybe someone will convince me.

If you are set on buying them, more power to you, but if you are at all handy, home-made racks are typically much cheaper. Also, you can custom build the rack to whatever you want the dimensions to be.