I say yes, but remember, do *not* skimp on the memory. I started with 4GB, and even sitting at the login screen and pressing "ESC" to make all 5 clients close caused a 20-second lag (sometimes more). Went to 8GB, everything is as fast as if I were running just one client.

I five-box with the 512MB version of the 9800GT, so you should be fine there. I use 1x22"(1680x1050, main maximized) and 1x17"(1440x900, 4 slaves in 2x2 layout).

I'm sure Dalaran could be smoother, but honestly it's 20fps+ on all clients and looks fine to me. If I raided in Dalaran, I'd care.

Wintergrasp doesn't lag (video) at all. When everyone is inside the courtyard and the WG match is almost over, that's a different story. It's still not local lag though. It's server-side lag. Can't fix that!