You DO want to overclock...right?
In that case, I would suggest different RAM, either of these kits will do fine:
G.SKILL 2GB (2 x 1GB) DDR2 800 (PC2 6400) $304.99
Team Xtreem 2 Gb Kit DDR2 (2x 1Gb) 4-4-4-10 800Mhz $305.00
Crucial Ballistix 2GB (2 x 1GB) DDR2 1000 (PC2 8000) $309.99
This will increase cost by about $75. However, you can easily save on the CPU and PSU without performance hits (with some effort, the E6300 will clock as good or better than the E6400)
CPU: E6300 $181.00 (saves $36)
PSU: 500W Silverstone (35A on the 12V rails
) $87.50 (saves $27.49)
The E6300 in combination with the P5B and good RAM will hit good clocks. You should be able to fairly easily hit 3.0GHz with RAM at 1:1. Possibly even better
Video card: SAPPHIRE 100189L Radeon X1900GT 256MB GDDR3 $134.99
In that case, I would suggest different RAM, either of these kits will do fine:
G.SKILL 2GB (2 x 1GB) DDR2 800 (PC2 6400) $304.99
Team Xtreem 2 Gb Kit DDR2 (2x 1Gb) 4-4-4-10 800Mhz $305.00
Crucial Ballistix 2GB (2 x 1GB) DDR2 1000 (PC2 8000) $309.99
This will increase cost by about $75. However, you can easily save on the CPU and PSU without performance hits (with some effort, the E6300 will clock as good or better than the E6400)
CPU: E6300 $181.00 (saves $36)
PSU: 500W Silverstone (35A on the 12V rails

The E6300 in combination with the P5B and good RAM will hit good clocks. You should be able to fairly easily hit 3.0GHz with RAM at 1:1. Possibly even better
Video card: SAPPHIRE 100189L Radeon X1900GT 256MB GDDR3 $134.99