...and so falls the other shoe.  Nvidia has announced the GTX680 Kepler series featuring 28nm fabrication and 3.54 billion transistors.  With 2GB of DDR5 RAM, and a 1006Mhz/1502Mhz clock (GPU/Memory), Tom's Hardware has referred to it as a "Hunter" GPU for gamers.

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Do want.

Same here. Only $499 for a flagship GPU, wow.

Yeah, i'm probably going to buy one, and sell my GTX580, rather than getting another 580. This way I can SLI 680's when I want to

There it is my future card...
Now Intel needs to put out the Ivy Bridge CPUs and all pieces are in place for my new pc.
And the benchmarks look promising, and so far no one moaned loudness of the card, unlike the GTX480.

I'm thinking about getting 2 of these babies and using the second one as a dedicated PhysX card. If the PhysX isn't impressive, I could always just go SLI instead.

Unless you are doing massive phyX stuff, I think lots of older Nvidia cards would probably do the Phyx job! Not speaking from a position of knowledge here however... but it seems rather a waste of a top of line card.
I believe you can combine a top of line card and use a cheaper one for PhyX, you only need to match them if you are SLI'ing.

Well yes, I am planning on doing massive PhysX stuff. Don't want to over-hype this up, but I've had this dream of mine for a while to have a serious physics simulation to play with. It involves probably thousands of objects, fluid simulations, etc. This would be way beyond the kind of "eye-candy" style physics used in normal games. Maybe what I am thinking is not even possible with current technology. But if it is, its worth the extra $500 to make this happen. Probably will wait until I have my engine somewhat working and max out the limitations of my current rig before I splurge on a new setup.