if you have a pc with CPU core 2 duo or higher, just need buy a GTX460 1G. don't real need buy a new PC for 1 game.
I have a Core 2 Duo E6600 overclocked to 3.0Ghz. I just upgraded to a GTX460 1G overclocked to 800Mhz Core, 2Ghz Memory. I have 4 Gb PC2-6400 memory overclocked to PC2-6666.
I'm getting 15-20 fps average with stutters down to ~5 fps in FF XIV. Other games run great.