$199.99 - evga intel x58 micro atx board
$39.99 - microatx case
$294.99 - intel i7 950 3.06ghz quad core
$81.99 - 6gb gskill ram
$79.99 - ocz 700w psu
$100 - evga GTX280

That's what i built last december for ffxiv when my old q6600/4gb/8800gts 320mb was strugglign to play @ 1920x1200.

I run windows 7 x64. I have a 300gb 7200rpm hdd from 5 years ago. I get 40fps in uldah and 60fps everywhere else. I have everything set to average/high, and I run 1920x1200 windowed only. I spent $800 on my system, and I could have skimped a lot of places and saved $200+ and still had the same system essentially.

If your system can't handle it, $600 will get you one that can play it beautifully. Also, I'm driving 3 28" lcd's, have a hundred chrome and ff tabs open, 2-3 rdp sessions, a movie playing, and a pile of other crap going when I play, and my system is barely batting an eye. It's been 8 months since I bought my box, you can get the same thing for a lot less now I'm sure.