If you are getting a whole new system, I would suggest Haswell. Great features and has upgrade potential later on with the Haswell refresh and Broadwell.
Well the Asus sabertooth 990FX R2.0 is overall a better board, it has more feutures, but also a better powerphase 8+2. on this board you can realy get high overclocks.
The M5A99Fx pro R2.0 is also not a bad board, it has 6+2 powerphase and digi vrm, still capable to oc the FX8350 to 4.8 ghz. with a decent cpu cooler, so the M5A99FX pro is a good board for some standard overclocking, if you prefer extremer overclockings, then pickup the sabertooth.
Yes it would be able to run a 780 or 770 on it. It would be good for upgrading for the next 2-3 years. Just remember most technology is outdated within 6 months or so.