if you want best performance and future proof then go with gtx 660. You can sli with it. But if you dont plan for any other card in future and want to save 1000Rs then go with amd 7870. But it is not worth according to my personal experiance. Bcs gtx 660 is better in performance and a better choice. Don't save little money go with gtx 660. Im sure you will never disapoint with gtx 660.
I hope it helps.