I'd wait until the game's re-rendered hardware wise D: there's still some poor coding done by SE. But they'll fix those issues. But it's up to you.

I'm on a GTX460 as well and it's just doing fine, the rest of my rig is pretty medi-core but nothing superior and I can play it. I'm gonna freak out though if SE is rising the #'s of displayed models/stuff and my gtx won't make up for that =3.
But I doubt that, that will be fixed by changing the RAM I spose.

Oh I haven't checked those PC rig links yet. Are there SSD somewhere? That thing made up some huge perfomance boost on my FFXIV D: or at least it feels like it.