2 cards is pretty much pointless unless you want to make a top-of-the-line PC for $2K+
otherwise it's just a waste of energy, you're better off with a better single card (they have cards that integrate 2 GPUs onto one card for just this reason)
Anyways I use a PS3 controller for my PC. You need to install custom drivers and it's pretty tricky/frustrating to get them set up (at least for me), but it's really cool. MotionInJoy drivers, they're called. There are several settings you can set the controller to, depending on the game you're playing, even a 360 controller emulator so that it works flawlessly with most modern PC games that implement 360 controls.
Also, KB/M isn't about preference. It's not like PC gamers just prefer KB/M over controllers because it's the "original master race" method or something... it's concretely and indisputably a more versatile control system for FPSes. If you're playing single-player or whatever then obv no one cares but if you're online then you're just gimping yourself.
--
_foolmo_
mobile computer