I think it will support six, although you might want to get additional clarification on that. Each card supports three displays according to Apple's tech specs.
You'd need to get a couple of relatively pricey scaler units since the 24" (and 27") LED ACDs can't accept DVI input even if piggy backed over a MDP cable. You'd need one of these for each DVI port if driving 24" LED ACDs or one of these for each DVI port if driving 27" LED ACDs.