CPU
- Intel C2D E8500 (3.16GHz/6MB/1333FSB) ~$325 (C WORLD)
OR
- Intel Core i7 920 ~$450 (CPL)
G/V card
- XFX 896MB GTX 260+ ~$305 (CPL)
OR
- Gigabyte 896MB GTX275 ~$355 (CPL)
RAM
- Kingston 6GB DDR3 ~$145 (CPL)
OR
- Corsair 6GB DDR3 ~ $165 (CPL)
Monitor
- 19" Acer X193HQ (1440*900) ~ $150 (CPL)
OR
- 20" LG W2043T-PF (1600*900) ~$189 (CPL)
HD
- Seagate 1TB SATA II ~$135 (CPL)
OR
- WD 1TB SATA II ~$138 (CPL)
These are the parts I have an idea about, I'm not too sure about Motherboard, Power Supply, Case & Cooler. I wouldn't recommend Blu-ray drive as 1) The average gamer wont need to use it often. 2) Pioneer Blu-ray drive costs ~$299.
With the cheaper alternatives: $1063, which leaves $437 for remaining parts. Assuming you already have keyboard, mouse, speakers, OS etc $437 might just cover the rest, although unlikely.
NB: OS will have to be 64bit in order to support 4GB+ RAM, if not, consider 4GB DDR 3