MegaMacs offers the refurbished Apple Mac Pro Intel Xeon 2.66GHz Workstation, model no. MA356LL/A, for $579.99 plus around $27 for shipping. That's $120 under our fall mention of a refurb (which featured half the RAM) and the lowest total price we've seen for any Mac Pro workstation with four cores. (It's also $253 under the best price we could find for a similarly-configured used model elsewhere.) It features two Intel Xeon 2.66GHz Woodcrest dual-core processors (four cores total), 4GB RAM, 250GB 7200 rpm hard drive, SuperDrive, NVIDIA GeForce 7300 GT 256MB graphics, and OS X 10.6 Snow Leopard.

A 30-day MegaMacs warranty applies.