New gaming system, but which GPU ?

I am going to buy a new Rig, since I've started gaming WoW, and I don't have a computer ATM..
I've already gotten some help in the homebuilt section about what hardware to choose, and the list goes like this:

mobo: MSI K9A-Platinum

CPU: AMD Athlon64 X2 4200+ 2.2Ghz

DVD-RW: Pioneer DVR-111D

RAM: Corsair, Twin2X 2x1024MB DDR2, PC6400 DDR800, CAS 5-5-5-12-T1, Twin2X2048-6400

Harddrive: Maxtor 250GB - SATA300 (Fluid) - 7200/16MB cache

power sup: nq4775-500s 500w

case: shg computers titantower

and now the question, which GPU should I choose if the only real gaming I am going to be doing for the next period of time will be WoW and The Godfather, I would like to be able to run both games at high resolution smoothly, but I don't see any reason why i should waste $500 on a top GPU now, when the DX10 cards will come out in a few, so my question to you is "what card should I pick?"
in the homebuilt section a user (WR2) recommended me to get a x1900GT, but that one card is unfortunately unavailable where i am going to buy my Rig..
would t he 7600GT "XXX" suit me well for the next year or 2 ?..
any help/suggestions are recommended

thanks in advance 8)

I've decided to go with the AMD, because i believe i get more for my money, I do have the funds to go top-end, but I don't think that's the best idea, since the new DX10 cards comes out, and the quad-core aswell, my budget is $2500 all inclusive (PC, monitor, mouse, keyboard, mousepad), but if i can save $500-$1000 I'll rather buy AMD, and still have the opportunity to upgrade with the AM-2 chipset, untill I'll change my whole setup to the Socket F..
I buy my stuff at www.shg.dk in Denmark, Since i don't know a whole lot about computers, I think it's a nice security to have an actual shop you can go to and complain if something goes wrong 8)

but of course, any suggestion with a good argument is appreciated, cause untill now I've actually only heard WR2's point of view..