Just do a normal build. You don't have to have special hardware to make it into a server. Even an old crap box could do. I'd suggest a low power 775 build. G31 chipset is perfect. Onboard GMA3100 integ, onboard LAN, basic ports, SATA, some have microATX form-factor.
RD-PC -//- i7 950 // Evga x58 SLI // 3x2 OCZ PC3-12800 // 2x Evga GTX470 // Corsair HX850 // SilverStone TJ07