Is it possible to run 7790 and R7 260X on crossfire. Also my current 7790 is 1GB, but I want to have 2GB VRAM so I will be going with 2GB R7 260X. Am I going to have problems with that?
yes; you can xfire them; no point getting one with 2gb of vram though. xfire shares ram, so the card with the smallest amount of ram sets the "max" ram for the xfire config. since the one card already has 1gb, the whole xfire config will be locked at 1gb of vram