As already stated WOW doesn't support CF.
Originally Posted by Max FPS
It drops to 30ish in cities. 60-140 fps everywhere else usually.
WOW is a very CPU bound game. Especially in large crowds and cities. You said you were getting poor framerates in cities, check your cpu and gpu utilization when your framerates drop.
I'm betting on a cpu bottleneck. Getting a better cooler than stock (if you really care about temps you should have already had an aftermarket cooler on there) and overclock the cpu and the cpu-nb on that 1090t.
Here is as article from anandtech on overclocking performance for the 1090t. Note the performance increase in SC2 (another Blizzard game) from 3.2/2.0nb to 4.0/3.0nb. FPS increase of 43%.
If it is a cpu bottleneck, adding a second 5870 or upgrading to a 580 won't help. Overclocking your current processor or upgrading to a newer Intel Sandy Bridge processor would be your best options.Edited by RichardS - 2/20/11 at 6:32pm