You might want to check the CPU affinities of the five WoW's with Task Manager and make sure that they are not all limited to the same two cores.

How much do you want to spend on a video card? The video card market changed radically two days ago when AMD released the HD4850 and Nvidia dropped the price of the 9800GTX to compete with it. Best Buy was selling HD4850's for $150 in-store yesterday. If you can get it at that price, it's the best deal in the history of video cards.