Hey Dude, What i did( i have 2x22" and a 20" monitor) i turned 2 monitors on their sides and split the screens in 1/2 res 1050x840. That way the 2 alts had a decent viewing area. you can rotate your screen using your video card control panel.
On my other monitor i have my main at full 1680x1050. I run keyclone and kavoom in my setup and it really works great. With keyclone using maximizer you can set so that your 2 alt windows will automatically change to 1050x 840 res every time.

Depending on your video cards you can should easily be able to run 3 wow on your main pc and 2 on your alt pc. >>> HERE is a picture of my 2 pc 3 monitor setup (this has improved alot since that photo must update). I also got the bug starting with 2 warrior/priest then 3 mages then went all out. I have a feeling ill be complete with my setup around the time i hit 70 :P

Hope this is of some help for you.

Peace out