Thor -
Just remember to buy a vid card that supports DirectX 9 and you should be fine. Keep in mind most benchmarks between ATI and Nvidia are even or within points of each other.
On the case of motherboards, I would buy one with all the bells and whistles. I thought of buying a basic MB and decided to go balls to the wall. I have Serial ATA, Firewire, USB 2.0, Digital output. Never thought I would use it, but I have my camcorder hooked into the Firewire; digital camera into the USB and a optical going into a cheap HT receiver. BTW, mine is a Athlon based system.
g