Well I'm just gonna give you my exact build
CPU- AMD Opteron 165 Denmark 1GHz FSB 2 x 1MB L2 Cache Socket 939 Dual Core Processor $300
Mobo- DFI LANPARTY UT nF4 Ultra-D Socket 939 NVIDIA nForce4 Ultra ATX AMD Motherboard $130
GPU- G71 $550
RAM- G.SKILL Extreme Series 2GB (2 x 1GB) 184-Pin DDR SDRAM Unbuffered DDR 500 (PC 4000) Dual Channel Kit System Memory $200
Fans- 3 VANTEC TD8038H 80mm 2 Ball Case Cooling Fan $30
1 Delta 120x38mm FFB1212VHE $25
1 VANTEC TD9238H 92mm 2 Ball Case Cooling Fan $10
CPU Fan- ZALMAN CNPS9500 LED 92mm 2 Ball Blue LED Light Cooling Fan with Heatsink - $70
CPU Thermal Paste- Arctic Silver 5 Thermal Compound - OEM $10
Hard drive- Western Digital Caviar SE16 WD2500KS 250GB 7200 RPM 16MB Cache SATA 3.0Gb/s Hard Drive $100
Case- Antec PERFORMANCE TX1088AMG Gray Steel Server Computer Case 480W Power Supply $130