If you get a ranco/johnson/temperature controller, it's a great idea! Controlling your fermentation tempatures greatly affects your beer.
Check out the sticky on sizing your keezer in the bottling/kegging thread- The only thing is, most people size with cornies in mind. Hopefully they're only one or two sizes you're dealing with, and it might help. Otherwise, I guess the only thing I can recommend is check it out for sizes of known freezers and stage your buckets to see if they will fit.