I disagree, if you are implying that the ~17% performance increase from a GTX780 compared to GTX770 or 7970 will suddenly allow you to max modern games at 2560x1440. None of those cards will max every game at 2560x1440 res without dropping graphics settings. You will still have to use FXAA and avoid SSAA in many recent games. Of course the GTX780 will have to compromise less but it stilll won't max them out.
I have a 7970 CF setup @1100/1550 and I can achieve 60 FPS average with ~48 FPS minimums, 2560x1600 res in Tom Raider with all settings maxed apart from SSAA. Even adding 2x SSAA would tank the FPS to mid 30s. A GTX780 (even overclocked) would get less than that.
My point is, that if a cheaper and faster 7950 CF setup @1100/1550 can't max out modern games at 2560x1440 then neither will a GTX780.
780 is a good card but it most certainly isn't a game changer for those who run 2560 res, it also isn't exactly "affordable" at £540