Skip the SLI'ed 6800's and go straight for a single 7900 or X1900, you'll get comparable performance from SLI optimised titles and games without SLI support will only make use of a single 6800 (the other will just sit idle), in that situation, a 7900 or X1900 will easely pull ahead and offer more bang for your bucks.
I'm curious to know what is in your current computer to get an idea of how much of an improvement you'll be seeing.
You are about to answer a thread that has been inactive for more than 6 months. If you still wish to proceed, please ensure that your posting is original and does not duplicate or overlap any prior responses to this thread.