What are the pros/cons of running 4 monitors on 2 video cards?

I've been running a homebuilt system with a Nvidia GTX260 for a little while with two monitors plugged into it, and I love it. Recently two more monitors came into my possession, and I decided to grab a spare ATI card I had lying around, throw it in my machine and plug in the two more monitors, just for the hell of it.



Now I know that theres solutions like SLI and that sorta thing out there, but that's not what I'm asking. I know I could go out and buy another GTX260, hook it up via SLI, and have some ridiculous power.



I want to know what sort of advantages and disadvantages there are in my having two separate cards that are different brands, things I need to be careful about, etc.



I mostly use my computer for gaming, graphic design, and video production.|||if u happen to buy another gtx260 and do some sli, u cant run multiple monitors while sli is enabled. u can only do that with the new 400 series cards. but what u can do is enable sli before running your game, then turn it off when your done playing so you can resume using your 4 monitors. if u happn to be interested in getting more power then get a gtx 465, 470, or even 480 if u want and swap that for the ati card and use it as primary gaming.|||With SLI enable you can 1 or 2 monitors at once but most games if any at all support more then 1 monitor