you can go for the 660 if you so wish...there won't be any bottleneck from your other hardware except your psu.
the 660 has a tdp of 140w if i m not wrong.
the 650ti also is an excellent card with the tdp of 110w and should not face the psu bottleneck even.

go to extremeoutervision.com/psu powercalculator for details