I am waiting till just before release and picking up a 680 or possibly 670 if they are out by then.The 7XXX series of AMD cards are pretty cool too.
I personally would probably go the 7870 close to the power of a GTX 580 with almost no power use. The GTX 680 does look incredible though .....
Ive already got a mATX build, that is an ITX board@Autti: It does indeed, I take it you are going a Micro-Atx build?