Your pc is totally fine, and you can run it on high settings for sure. Ok, now about the Alienware machine. Currently, FFXIV Beta is maxed at 30 fps, and they don't have multi-GPU support yet. Also, there is a very nice graphical option called Ambient Occlusion, but they are still working out the drivers and all the bugs causing flickerings, black screens, blue screens, etc..., so turning that off Ambient Occlusion actually gets you better frame rates. If you're not in the beta, sit tight, and stop worrying so much.
The japanese HP promo, getting people beta keys if they buy their "FFXIV Adventure ready PC" only have a GTX 260 card. So any card, above or equivalent that, should be fine on medium to high settings by release.