compare these gpu's, gtx 660 and r9 270x, link below

R9 270X and the hD 7870 GhZ edition is much faster than the GTX 660. I don't think watchdog is really a something that should pull you to a GTX 660 really since the price of games decreases over a short time from release. Plus R9 270X offers you 2 games from AMD games list:
http://sites.amd.com/us/promo/never-settle/Pages/nsreloadedforever.aspx


GTX 660 is a reference model so it will be hotter and louder than the other two.
 
Solution
The difference is minimal.

http://www.techpowerup.com/reviews/ASUS/GTX_780_STRIX_6_GB/25.html
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