GTX 660 should be as good as gtx 480 which is the recommended GPU part on both of the games.
Usually recommended line is where you can get 45-60 fps with atleast 1280×720 on high settings. However this varies between each game and each build. You didn't tell anything about rest of your PC, CPU, RAM and such is very important too when it comes to valuating how well it runs games.

To help you further, here is some benchmarks for you to check out

Thanks so much, mojangsta! :D

View attached image.

Thank you~

Thank you.

Thank you :)

thanks ^^

Thank you for the awesome giveaway Mojangsta! :)

Thank you the reduxes Mojangsta!:0

Thank you :)

Nice, thank you!

Thanks for the giveaway! ♥

T.Hanks!

thanks

Thank you!

Thank you.

Thank you :D

and I wonder if my HD 5850 will be enough ^^

thanks :}

thanks!

thx

Thank you. Your GC should be fine!

thanks a lot for the chance

Thanks buddy.
I will also try your puzzle. :)

Awesome ( ° ͜ʖ͡°)

Thanks for the giveaway!