The excavator cores were never any good for gaming even at launch.
As for performance issues all the games pointed out as examples of stuttering or low fps are heavy cpu usage games i.e. any bf multiplayer, large open worlds of fc 3&4 and strategy games with large numbers of units (like the total war series).
oblivion works brilliantly with everything maxed out (i don't have skyrim).
witcher 2 is also fully playable with ssaa off.
^ yup worse... equally performs same as what GTX 650Ti
if you're getting lower frames with a 280x at the same res. and settings than a 650ti then i'm pretty sure you've not done a clean driver install. you're stating that a 650ti matches or beats a 280x when paired with an athlon x4 which makes no sense.
@op; don't get a 270x or a 280x they are both at the end of their product cycles.
yes, the cpu will be a bottleneck but plonking in an overly powerful gpu should not cause performance to drop from current levels.
all you need to do is take 2 mins to turn down cpu based settings of a game.
Your cpu is going to end up getting replaced anyway - if soon, then get a gpu to match the upgrade you're planning on.
If you're not going to be changing your cpu in the next 12 months then go with a gtx 960.
i bought my 280x with a plan to get an i5 at a later date.
Basically my experience has been that a fast gpu allows me to crank up the details at max res and if i face issues i just turn down the offending feature which is usually physics/rag-doll effects.
if i want more frames then i just put aa down a notch.
i've NEVER had to reduce my resolution to get playable frame rates.
a mid range gpu will restrict you to AT BEST average performance (~40fps) and quality settings which is the same performance i get - only difference is way better image quality. also when it's time to upgrade you'll have to spend on both cpu+gpu again. if i want to play dragon age today, i only need a cpu upgrade. had i opted for a more sensible i3+270x last year i would have spent more money to get the same performance at lower quality - and still require a complete overhaul of cpu+gpu if i wanted to play dragon age (or any recent aaa title).