**Disclaimer** I have a 280 OC in the mail on the way to me right now...

Currently I run 2 video cards, both with 2 DVI outs. I run 3 monitors, and typically run my main client on the center monitor, the slaves on the right monitor and I use the left for research, etc.

I've run several configs
#1: 8800gt running center and right monitor, 7600gt running the left.

The slaves seem to run fine, the main monitor is a nightmare in dalaran in that configuration

#2: 7600gt running center and left, 8800gt running the right. Much better, at least bearable in dalaran. Non issue for slaves.

#3: 8800gt running the center and left, 7600gt running the right. Pretty much the goldilocks zone. Slaves are slower than in config 2, but they really don't need to run that well. Main monitor no longer has issues during hectic fights.

My 2 cents/conclusion - I'll never run multiple monitors off of 1 card anymore.