You can find a lot of fairly powerful, refurbished servers on eBay for not a lot of money. Check out for example the Dell PowerEdge CS23-SH 1U rack server from CharlesComputers, available for £559, a price that includes delivery and 549 Nectar points.
That server comes with two quad-core Intel Xeon processors, L5410, which are clocked at 2.33GHz. These have 12MB cache each and a 1.33GHz FSB. They sit on an Intel S5400SF motherboard with RAID support and a Delta TDPS-600CBC power supply unit.
The Xeon L5410 was launched back in 2008, is etched on a 45nm lithography and has a TDP of 50W only (which translates into a low power dissipation).
Other features include 64GB of RAM (that’s 16 4GB PC2-5300F fully unbuffered memory modules, which means that there are no banks free), three 3.5in SATA caddies which can accommodate up to 6TB of storage space and a 1U form factor. Connectors include two PS2, three RJ45 (including two GbE ones), VGA port and two USB 2.0 ones.