If you need 2 catleaps, then you need a new card. It needs to have 2 x Dual link DVI outputs, where your current card only has 1. So you could just add 1 catleap with all your current stuff, or 2 if you get a new video card.
2 random cards from googling - not endorsing these, just showing you a few that have the feature. I'm sure there are plenty more.