Take a look at my specs for the new computer I plan on building. The software will be used for Sony Vegas, Adobe Studio 8, along with some other software that will be able to utilize the system. The system will be based on videoguys DIY5.
Intell Core2Duo 6600
Kingston 1GB 240pin DDR2 PC2 6400 (x2) KHX6400D2/1G
WD2500KS 250GB SATAII
Hitachi SATAII 250GB x2
Thermaltake Eureka VC8000BWA
eVGA E-GeForce 8800 640mb
The only things I really changed was the video card along with going with the 6600 processor instead of the 6700. The performance dropoff is not that much and it still has the 4mb of l2 cache. I am still researching sound cards, so while reviewing my choices if you have any ideas on what to get for a soundcard let me know.
you dont need any special sound cards for video editing, the sound card thats built on the motherboard is fine. the video card you selected maybe a bit overkill unless you are planning on doing uncompressed HD or animation type stuff.