Some points:
1) I went to that link. The EVGA 4GB models are way, way overpriced.
2) As mentioned, 4GB is not needed. You're better off with a FASTER 2GB card (or cheaper 2GB of the same performance).
3) The very BEST GTX680 is the Asus GTX680 TOP (aka "DC2T") model. I own this one:
http://www.pccasegear.com/index.php?main_page=product_info&cPath=193_876&products_id=20326
*This Asus is 3-slots, but it's the fastest and also the quietest card due to its very large cooling solution. It doesn't even bend because it has a backplate. If you want a 680 this is the one to get.
4) AMD however has some great deals (Crysis 3 and Bioshock included with some cards). If you've got the money, the HD7970 GHz cards are good.
*You need to investigate these games as I see no reference here.
There's a big range in price on the HD7970's. There are HD7970's and "HD7970 GHz" edition cards.
For example:
http://www.pccasegear.com/index.php?main_page=product_info&cPath=193_1309&products_id=19553
This is another 3-slot and is an HD7970 yet is capable of overclocking to 1000MHz while still being fairly quiet. A great value (especially if those games are included).
Summary:
- investigate the free games
- relative performance in this order: HD7970, GTX680, HD7970 GHz (varies within models too)
- NVidia or AMD? (Pros and Cons)
- Best GTX680 is the Asus GTX680 TOP
- Best HD7970? (Pros and Cons. The 3-slot Asus would be my choice. The 6GB Sapphire is too expensive)
Final note:
If those game coupons aren't available it makes the decision much harder. In a few games the AMD architecture does pull ahead, on the other hand there is a fair amount of evidence that AMD cards tend to stutter more with the NVidia cards providing more consistent frame time performance.
Cheers.