I second a hackintosh render farm. Literally 50% less price and easier to maintain (working with internals since you are going to open all the mac minis unless you want to pay Apple’s big markup prices for RAM and storage.
My revised Hackintosh has been amazing stable on very low end parts – first one has a non-recommended board that I already had lying around. It was trouble. I got a recommended board and with same CPU and it runs FCP, CS5.5, Streamclip and more without a hiccup.
From: After Effects Mail List [mailto:AE-List@media-motion.tv] On Behalf Of Tim Sassoon
Sent: Monday, November 12, 2012 4:25 PM
To: After Effects Mail List
Subject: Re: [AE] Semi OT: Yet another mac mini render farm thread
The power supplies are internal now. And the current design is much better than the old, which were quite good. Especially now with i7's and Thunderbolt. We use Minis for servers, they work great. Treat them like blades. At the two-year mark, still under AppleCare, put them on eBay, recover half the cost, and drop them into a USPS Medium Flat Rate box and send them anywhere. You don't even need to buy the server version anymore, since OS X Server is only $49. Or it was - just tried to find it on the Apple Store and failed.
if you go with mac mini's try to get a few spare external power supplies from apple