Adding another Video Card to a 4850x2 Setup

Hi Folks,

Painfully newbish, but I'll try and be thorough to avoid wasting anyone's time. Few months ago I purchased a Dell XPS 730x. Basic stats as follows:

OS: Windows 7 64-Bit
CPU: i7 940@ 2.93 GHz (Bloomfield 45nm Architecture)
Ram: 6.0 GB Triple-Channel DDR3 @535 MHz
Motherboard: Dell Inc. 0P270J (Intel x58 Chipset)
Graphics: ATI 4850x2

The computer showed up and was setup with Crossfire enabled and they had caps on the two DVI outputs of one of the Video cards. I currently use two 24-inch monitors and disabled crossfire in order to hook up my TV as a third monitor for watching movies and whatnot.

Even though I don't really do any serious gaming, I have this weird OCD habit of making sure that should I decide I want to invest some time in gaming, I won't be held back by my hardware. ANYway, I'm trying to find out the best way to go about having these three monitors hooked up to my PC AND still have Crossfire enabled.

I understand that that's pretty much not possible with my current situation, but I'm looking for suggestions on what I should do in the not too distant future to make this a reality. Can i just add yet another graphics card? Could getting a cheaper card negatively affect the performance of my current setup? Are there any compatibility issues I should be aware of regarding drivers if I should buy a different model graphics card?

It looks like I only have one slot left on my mother board and I was hoping to get a TV/Tuner card put in eventually...but I suppose I could always go the route of one of those HD Homerun things. Anyway....any and all suggestions highly appreciated!

-C