Well there are a few things:
1.) Intel's Core 2 is much faster than the Athlon 64. It'll stay this way till K8L comes out, which is a masssive upgrade of the A64 (K
. When this update comes its hard telling, so I'd personally suggest you go with an Intel based system right now. its simply looking to be the better platform.
You can grab a $300 Core 2 and get FX-62 performance for 1/3 the price.
2.) There's a reason why all the high end boards have Nvidia, they're better for the most part. If you're going to go AMD then you'll want something like a Nforce 590. If you're going to change and go with Intel (which I recommend) then you're going to want to look at the 975x I believe is the chipset name.
3.) ATi will be releasing the X1950XTX (X1900XTX with GDDR4 memory at 2.0Gh!!). It'll be the fastest single core card out there. The thing is that we're not to far away from DirectX 10 cards, G80 is some time in October most likely and R600 from ATi is not that far away. So if you want to wait or maybe buy a lower end card for now (say something like the upcoming X1950 Pro, which is based on Rv570) then I wouldnt blame you.
4.) 2GBs of rame, you'll want 2x1GB of course.
5.) Since you have such a large amount of IDE drives then you might have to look at a seperate controller cards. Intel is completely removing IDE support from their chipsets, Nvidia and ATi are slowly phasaing them out. So a board with enough connectors might be hard. They'll be there but not directly in the chipset.
6.) AMD and ATi just merged but its awaiting stock holder approval (no reason why this shouldnt go through) and you wont see benefits of this relationship for another few years.
Basically this: I highly suggest you consider going with an Intel processor, the Core 2 6600 to be specific. It out performs the fastest processors from AMD at 1/3 the price.
Also, if you want to buy the highest end card by the time you build the system then you'll be looking at an X1950XTX.