I didn't realize the new ATI cards woudl let you run three monitors (with those caveats). That sounds like a great solution to me because I'd much rather run it all on one box.

With that in mind, I would probably use my 30" for the main wow instance and two 24"'s rotated for the slaves. Assuming I kept the slave's at low res, do you see any problems pushing those pixels out of one card for three large monitors like that?