Yes, The 7800GTX is the best card out right now. The R520 is coming out around october i think. The truth is no one knows which one is going to destroy the other, I think the R520 is only going to have 16 pipelines now too. Anyway, If you cant wait to see the results of the R520 its not a big deal because the 7800GTX is a beast and will handle anything right now anyway.
Yes, AMD 64 3700+ San Diego is a great processor.
I havent heard much about the ABIT Fatal1ty board, all i know is its expensive, a good board that i know is the DFI lanparty Ultra D, especially for overclocking.
Gigabyte EP-45 DS3R
e7200 @ 3.2
Corsair VX 550