mmm I second the vote on the GTX 770. It outperforms the 280X at 1080p by a negligible difference. I also bought the 770 because the upcoming games are working alot more with Nvidia so a better optimization for Nvidia cards. I hardly see AMD doing the same only recently with mantle. It'll be long before a good amount of games will actually use mantle.
If the price difference between the 280x and the GTX 770 is too large then get the cheaper one. However if it's something you can handle then definitely get the 770.
BTW if you do get the 770, I'd prefer something like Gigabyte, MSI or EVGA rather than ASUS