I don't have all my characters up in the photo, I was pvp'ing on my druid and running my AH bot.

The main computer is a Core2Quad, GF8800GT, 2g RAM, 24" Widescreen LCD. My druid tank is on this one.
Left computer is an older one; AMD Sempron 2400+, GF6600OC, 1.5g RAM, 17" LCD. My priest is on this one.
Right computer is a Core2Duo, GF7900GT, 2g RAM, 20" Widescreen LCD. Got 3x elemental shaman on it.

Keyclone only on the right computer, multibox on all 3.

I originally tried running the main on the left and 4-boxing on the right, but the framerate wasn't acceptable to me so I bought the C2Quad and now everything is happy .

If the left computer could run 2 instances of WoW I'd get another 20" Widescreen, because having 2 of those in portrait mode is just sexy. I've thought about putting the right one in portrait with 3 divisions instead of 2, but it doesn't fit on the desk that way.