Dual boxing is so much fun but stil very limited.

i am considering to go for 3 boxing instead since my hardware can only support so much.. but i hav been thinking for some days.. what should be the best 3 boxing team that can really do so much more than a 2 boxing team..

any suggestions? i think one of my toon will be a pally or warrior since they can tank and i can forget bout them while i change to other char to cast spells. like my current pally/mage, i could leave my pally there and switch to my mage to spam blizzard...