Yeah for the graphics I would pick ATI as well... mainly for the reasons that William has suggested...
But what about the monitor to completely utilize what the GPU has to offer? For me I think it would be something like the Apple 30 inch or perhaps the Dell 30 inch LCD. Or may be get both and create a dual view set up
(you'll need a wireless keyboard and mouse as well, so that you can see what's happening on both of them without turning heads...). Okay this is not realistic (especially with the money you are spending on this this you can probably get a car for it
) but it's cool to dream about it anyways...
And may be some Raptor hard drives (even though they might make some extra noise, it's all right I guess). Oh yeah btw, I hear that the LCD temperature display doesn't work that well... oh well but it looks cool so I guess it's good to have in any dream computer.