hi guy i like to know if this gpu XFX ATI Radeon HD 6790 is better then what i got witch is asus radeon hd 7770 in dual crossfire, due to the 6790 its going cheap in ebay and the fact is im getting problems with fps in most of my games with my 2 x 7770
Guys what are you talking about?The HD 6790 is slower than even one of his HD 7770's and it won't perform any better in high resolutions with AA because it has 16 ROPs which effectively makes it perform like a card with a 128 bit memory bus.
And even if he has problems with Crossfire he can awlays turn it off and use only one of the cards.This way the problems are gone and he still has a card faster than a HD 6790.
Also HD 6790 in Crossfire is SLOWER than HD 7770 in crossfire.It's slower when its a single card and also scales worse.
If you want an upgrade from the HD 7770 the absolute minumum you should consider is a HD 7850.Even that will be slower than your cards most of the time.
So then, no, the 6790 would not be an upgrade path, unless your gaming in DX9.
Two 7770 in crossfire managed similar performance as a single 7870 according to the tests done by www.techpowerup.com, averaging 22 and 22.4 fps respectively in Metro 2033 at 1900x1200, so if your using DX11, then I'd suggest getting a pair of 7870's for $260 each if you're looking for significantly better performance, or a pair of 7850's for $210 each if you want a moderate performance increase.
I think your best option, however, is a single 7950 for $320. It will offer better performance than the 2 7770's you have now, and you can get another 7950 card in 6 months or so when prices drop.