I am currently running two MSI Radeon 4850 gpu's in xfire, would it be better to upgrade to a 5780 or a 5970 (saphire)? My resolution is 1920x1080. System specs are:intel E8500 cpu,4gb of 1066 team extreme ram,Gigabyte GA-EP45-DS3R motherboard,500gb sata H/drive, thermaltake 750watt Toughpower PSU all in a Antec P183 case. Any help would be appreciated!!! Cheers BLU.