Apologies, i lied!! Apparantly the 5xxx series all support 3 monitors...the only problem is below the 5750, they have 1xVGA, 1xHDMI & 1xDVI connectors...which is a pain. The 5750 however, has 2xDVI and 1xHDMI...which would be my recommendation.
Thanks for the advice, the only issue I've heard with the ATI cards, are in order to run three monitors they all need to be the same exact resolution and refresh rate? Is this true?