2 760s are going to be way faster, however you might run into sli related issues.
he,s not talking about 760,s but 660ti,s.
and the are still faster then a 770, the come with 192 bandw.
so i would go for 1 gtx 770 and upgrade from there.
In the title he said 660tis and in the post the said 760s, that's why I said 760s.