I have a GE 5 cu. ft. freezer that I use for fermentation and for storing corny's. (http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053
Easily fits a 6.5 gallon carboy and can fit 2 corny's without any mods. If you add an 6-8" extension to the top of it it will easily hold 3 corny's and a CO2 tank and will allow you to install keg taps if desired.
In my opinion this is the most bang for your buck if you're looking for fermentation temperature control and the ability to store kegs. Of course you need to invest in a temp controller, but for $79 its well worth the price of being able to dial in your fermentation temps to whatever you want.
I've got a bock fermenting away in mine right now at a solid 48-49 degrees