you could wait for next gen gpu's but not really worth it there will be only a slight increase in performance like from 400-500 series and the 670 can play all games maxed out anyway so why guy anything else
when it comes down to it the 660ti is using the high end chip the 660 isnt so marginal performance boost but better stability in overclocking and you can ramp it up even more
the Evo is okay if you dont plan on overclocking to much but if you are going to be overclocking get a corsair h80 or h100 or maybe a dual tower air cooler