what size fridge for ferm cabinet

So i have been crusing ebay, CL and looking around town for a fridge to tear apart as many have done here to build into another cabinet for looks and space reasons. What I am not real clear on is what size I should be going after.

In general I am looking to build a 2 ' x 2' box 3' high. It will probably be 4 + cf. Now I could just get a 4.3 CF fridge, but can I get away with a 3.2 or less and still be able to lager in it? Granted this all depends on insulation and everything but I have seen everything from 1.7 to 4.3 fridges so i am just looking for some guidance.

Mine is one of the mid size ones. Cooks to 60 easy. With about the same siZe fermetation chamber attached ( large enough for 4 buckets). I'm guessing it's a 2.7cf or 3.0. No need to get a larger one. Mine happens to be exactly the height of bucket plus airlock too.

Edit : whoops didn't see you want to lager.

I would like to start fermenting lagers and I can only get one keg in the serving fridge without taking the door off. Which i'd rather not do.