Currently i have HD6670 1GDDR5 ... its working file except in some new games that i cant play at ultra high
i need a new VGA to cross fire with this one ...
new VGA should be better than this one so i am looking for the best possible option with lowest price possible ...
my system specs are :
CPU : AMD X4 980BE @ 3.9Ghz
MB : ASUS M5A9PRO
RAM : 4x2GB DDR3 @ 1066
PSU : QUEEN 580W
You don't understand how Crossfire works, Crossfire for 1 is only ATI/AMD cards, I think you get that, But you can not crossfire a 6670 with a 7770. But you can say crossfire a 6650 with a 6670, Or like the 4 series cards for ex. You can crossfire a 4850 with a 4890, or a 4870 with a 4890, or a 4850 with a 4870. They are pretty much the same cards just with a few minor differences, while a 6670 and 7770 is just different, can't crossfire.
So if you get a 7770, only card you can crossfire with a 7770 is a 7750, And they don't have to be the same brand, ! could be Gigabyte while the other is HIS, they will work.
I would recommend something like a HD7850 2GB or better from AMD, or a GTX660 from Nvidia if your wanting to max game settings out. single 7770 would walk all over your 6670, but it will have problems maxing newer games out as well at even 720p
Also, Make sure your board can run Crossfire/SLI If it can run just crossfire I would get an AMD/ATI card, Some AMD boards can't run SLI (Nvidia cards), Thats if you plan to run 2 cards later.
PS: You can run a 7770 as a main card and run the 6670 for say 2nd monitor, but it wont be used in games. I run 2 5850's in crossfire and run 1 HD6450 for a 2nd monitor because of the 5850's dual monitor flicker problems, So 3 cards total 2 in crossfire (5850's) and 1 doing nothing but desktop 2d work (6450).