OCZ powerstreams are good... don\'t get anything less than 420W, and get something that gets good amps on the 12v Rail
PowerPC & Cooling make the best ones, but they are way too expensive.
Good luck with the new build. I just built a dual core Opteron and it destroys my old 3000+ You could also check into the Intel 9xx series dual cores, they are pretty good too... but the smart money is on the AMD X2\'s.
What programs do you use the most? Might be able to find some benchmarks to see the difference.
As far as matching up parts... i\'ll use AMD as an example
ATX Case - ATX is universal, just make sure it isn\'t micro ATX
X2 Processors are Socket 939, so make sure you get a motherboard that is socket 939 as well.
Motherboards now have 24 pin power connectors, but a lot of power supplies come with 20 pin output connectors. It\'s not a huge deal, a 20 pin will work with a 24 pin, but get a PSU with a 24 pin motherboard connector.
Also make sure your motherboard is PCI-e, and pretty much any Nvidia & Ati card has Dual DVI outputs. ATI acutally has the better image quality, so for video editing they would probably be the best choice.
As far as memory goes, get at least PC3200, 184 pin DDR SDRAM, dual channel (pretty much all of it is dual channel). Thats the standard for AMD X2\'s and Athlon 64\'s in general.
2 x 1GB sticks is quickly becoming standard, you might want to get even more than that if you are doing heavy video editing.