Assuming you're in the US, you can customise servers on TigerDirect.com and i have tried a custom build, with the following specs:

Intel P4 CPU 630 3.0 GHz/800FSB/2M S775

1GB DDR2 4200

2 x 400gb SATA drives

1 x 250gb SATA drive

So that is a P4 3.0Ghz, with 1gb of 553Mhz DDR2, and 1.05TB across 3 drives, so that you could implement RAID 0. And it is in a standard ATX case.

Price: $1,569.96

Just an idea, you can customise your own here: Here

Liam