660 ti 3gb vs 670 ftw sig 2 (revised)

Ok so i picked out these 2 cards and its not really a matter of which is better but HOW MUCH better the 670 is would it be worth the extra cash  or should i just get a cheap card and hold out for the 700 series.  Also a guy already recomended a radeon hd 7970 below what are some arguements for/against that pption i like mostly shooters so i would be playing crysis 3, CoD, might try some more but my number one game is league of legends which doesnt take much so im sure all of these cards can handle that

 Think i might want a second monitor too so i can have my game on one and my other junk on the other one

here they are

Gtx 660 ti 3gb - http://www.newegg.com/Product/Product.aspx?Item=N82E16814130812

gtx 670 ftw sig 2 - http://www.newegg.com/Product/Product.aspx?Item=N82E16814130843