GPU Suggestions: Buy second card for SLI or a new Gen card?

I'm was wondering what would be the best use of my money.

My current specs are
CPU: Intel I7-3770k @ 3.5 ghz (3.9 Turbo)
Memory: 16 gb DDR3
Screen Resolution: 1920x1080

I currently am running with a EVGA 02G-P4-2680-KR GTX680. As the cost is about the same should I get a second card and run in SLI or should I get a new 960GTX?

I'm not sure of the gain in performance one way or the other?

 

Believe it or not but your 680 is actually oveall more powerfull than a 960

http://www.techpowerup.com/reviews/MSI/GTX_960_Gaming/29.html

 

How are the prices of 960 comparing to 970?

 

It is always better to go with one card when possible.
Multi-GPU systems tend to make problems with most applications, especialy with rF2. Forum is full of problem reports....
960 won´t give you a great advantage - if at all - over a 680.

 

960 is around $200 USD
970 is around $350 USD

I'm hoping to keep it around the $200 mark. The GTX 680, on ebay is around $210-$250 give or take.

 

Sell you 680 and get a 970. Done, close thread, jk!

 

Would a 970 out preform an SLI 680?

 

SLI is pretty much broken in RF2 unless you play in Nvidia 3D Vision, which, by the way, is AMAZING with RF2 (and most other sims).