Rate my upcoming PC configuration

I am planning to buy a new desktop PC with the following specifications. I will install Visual Studio, Expression Web, Windows Vista, Windows 7. I will not install any games.

Processor - Intel Core 2 Duo E8600
Motherboard - Intel DP35DP ATX Motherboard
RAM - 8 GB DDR2 (CORSAIR/Transend)
Hark Disk Drive - Seagate 3x500 GB
Graphics Card - EVGA or Palit 9800GTX 512 MB
PSU - CORSAIR CMPSU-1000TX 1000W
Cabinet - Cooler Master – CM 690
Cooler - COOLER MASTER V8 CPU cooler
Monitor - ViewSonic 22’’ VX2255wmb
DVD - LG GGW-H20N

Should I buy core2quad instead of core2duo?

Will I get significant performance boost if I use a quad 3 Ghz instead of duo 3.33 Ghz in Visual Studio 2008, Windows Vista, Windows 7.