Big chance of bottlenecking (depending on the game) the CF setup esp. with those CPUs at stock speed. The power requirement/heat would also be an issue with the CF.
If you'd/he'd be gaming in a single 6950 in 1080p with the 860K/880K on AAA games, definitely have to lower in-game settings to get respectable framerates: https://www.youtube.com/watch?v=Jw3QqhBfuco.
The better option now is to use the single 660ti instead (will beat the single 6950) with lower power requirements.