I just looked at a review done at
www.tomshardware.com on SLI/6800/7800.
Their conclusion was that 2x7800 in SLI mode was the way for any serious
gamer to go.
However, in every benchmark I saw except for the 3Dmarks ones, the 7800 SLI
setup produced fewer fps than a 7800 in single mode. I can't understand
why they push the SLI mode 7800 setup.