Hey it's always nice building a new system
Depending on your budget, I'd say go for the following:
Processor: Core i7 I7-920 Quad Core Processor (2.66GHz, 4.8 GT/s Bus, Socket B LGA 1336) - Approx. $280.00 at ZipZoom or TigerDirect.
Motherboard: ASUS P6T Deluxe V2 - Approx $290.00 at Newegg
RAM: OCZ Gold 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 - Approx $100.00 at Newegg
GPU: GIGABYTE GV-R487D5-1GD Radeon HD 4870 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready - Approx $170.00 at Newegg
Those are the main components all based on current technology. I prefer NVIDIA GPU's but the ATI above seems to be good value. I'd say steer away from the Intel socket 775's as they are getting old now and stick to DDR3 RAM for the same reason. I think make sure that RAM is on the motherboards Memory QVL list but I can't see it won't work.