Dual boxing / dual card question

Hello all!,

I'm new to the site here and was very fortunate to find it as well, just want to ask a quick question about dual boxing with dual cards, I'm also pretty sure it has been asked before.

I dual box with multiple games: wow, eve, and APB.
I currently have a set up with two 7970's crossfire bridge is installed and disabled with a 3 monitor set up right now, 2 big ones I use for playing games and the third is a chat window for steam etc. All 3 monitors are plugged in the top card, why because when crossfire is enabled the ports on the 2nd card are "off".
Would plugging the 2nd big monitor into the 2nd card increase FPS and performance? Because a 2nd client of which ever game I'm playing is ran on the 2nd monitor would that 2nd card take the slack off the 1st card?

I hope I explained what I'm asking for right, lol.
If you have any questions just ask me.

Yes, both World of Warcraft and EVE Online natively support the option of running the client off of any display adapter attached to the system (I have no idea about APB). One caveat is that you can't use DX11 in WoW on a monitor that isn't attached to the primary GPU.