yea, the two companies don't play well with each other, SLI is an Nvidia term and Crossfire is an ATI term, they cannot be mixed (except for the few hacks that might work, but there are no guarantees ). A hint of advice though when upgrading your system, research these types of things before you order something. Doing that can save a lot of headache and money, especially in the computer world where everything is always changing.