I nearly sh*t my self when i saw the recommended requirements for the game... I was thinking well that didn't take long at all for the usage for the new hard ware. ( New Nvidia Cards )
Pulled From You - Gamers
NVIDIA GeForce GTX 460
Intel Core i7-920 (2.666 GHz)
Does the game support SLI/ Benchmark version
NO - http://www.gamespot.com/pc/rpg/finalfantasy14/show_msgs.php?topic_id=m-1-55598674&pid=960613
NO - http://ffxiv.zam.com/forum.html?game=268&mid=127799045820802637&howmany=50
N/A - http://ffxiv.zam.com/forum.html?game=268&mid=1279305081101848307&howmany=50
Maybe Soon - http://ffxiv.zam.com/forum.html?game=268&mid=127695734122246145&howmany=50
I cant really say it will use SLI, or if it doesn't. Either way some of the links i posted say it will come out with SLi support/CrossFire.
Either way you should go with the Gtx 460 SLI. Either way you'll be saving money. From what i read the difference between the GTX4xx serious are only a few frames less about 2-5. I would go with the GTX 460 SLI. You will be getting more power. For FF XIV, im sure Sli support will come out. If you are really unsure of this sistuation. I would wait it out, but for the most part im positive they will release SLI/Crossfire. After all the benchmarks don't detect the 2nd GPU. So maybe the full game does support it.