GTX 660 TI SLI or GTX 780 for Battlefeild 4 3D gaming?

Hey I recently bought a Benq monitor with 3D capabilities and want to put it to work. Currently I have a GTX 660Ti and can play on Ultra at 45-70 fps. (Estimate maybe more). I was just wondering if I should go SLI with the 660 ti or splerg on a new graphics card. Also I have a i5 3570k cpu (just saying just incase that will give me trouble for 3d gaming). Also if I go SLI my pci ports would be 3.0 x16 and a 2.0 x8, would i get the full potential out of the 660ti's? Thanks!

My monitor is 120 hz what kind of fps should I expect?

 

I can get ~110fps easy with 2 regular 660s on high settings @1080p. You should be able to do much better with two 660 Ti's.

 

My 780 get me around [email protected] 1080p on BF4 in ultra settings, bearing in mind it's the phantom edition (in other words 780 is overkill and that why I like it.)

Do you think my i5 3570k would bottle neck a 780?

It may hold the 780 back a bit but it should fine just playing games and such.

660ti sli and 780 performance are nearly equal. It is just a matter of if you want to pay an extra 400 for the benefits of a single card solution. Assuming you have the psu for sli.

Thanks Guys for all your feedback, im still in a dilemma on either to buy a 780 or another 660 ti. If anyone has any other ideas im open to try!