Check out this HP Proliant DL585 G2 rack-mounted server from eBay high end server specialist, Bargain Hardware. This vendor is currently selling the G2 version of this product for £445, including delivery and 420 Nectar points.
The server comes with four dual-core AMD Opteron 8220 processors, each clocked at 2.8GHz with 2MB L2 cache per CPU. There's also 32 2GB memory modules (PC2-5300P DDR2 ECC models) leaving no free DIMM slots.
Other features include HP Smart Array P400/512MB hard disk Controller (in a PCI-Express slot), eight 2.5in SAS or SATA hard drive bays, two redundant hot swappable power supply units, a DVD-ROM drive, an integrated ATI-RN50 video chip with 32MB memory and two embedded NC371i Multifunction Gigabit Network Adapters with TCP/IP Offload Engine.
Expansion capabilities include nine expansion slots (one reserved for the GbE adaptors), four USB ports, two VGA, two PS2, one serial and one ILO.
According to the description, this is "ex-corporate item which has been removed from a fully working environment. The machine is in excellent condition with no noticeable surface marks or scratches." It doesn't come with any form of warranty as well other than "dead on arrival".