Hello! I'd like some advice on new GPUs. Basically I'd like to prepare for Rome II and also Planetside 2.

What I have right now is the following:
System Model: MS-7522
Inte Core i7 920 Quad Processor
Corsair Powersupply 750W
Corsair Dominater DHX+ DDR3 6gb ram

GPU: Asus Geforce 560ti 1gb

What I've been looking at is the ZOTAC Geforce GTX 670 2gb. And basically I'm just wondering if it's worth my money? Or should I go 660 instead or perhaps pay the extra money to go for a 680?

Note: Not too fond of tinkering around!