Single 1080P and crossfire is an overkill unless you are trying to set records, averages about 10% performance loss compared to X8 X8 with X16 X4.
The Q6660 Inside
No, There is no bottleneck , The 960T when unlocked and OCd is enough for the setup above for at resolutions up to per say ~ 2560x1600. It all depends on the Resolutions. PS: If you are going to get a new AM3+ mobo, it would be a good idea also spend some of the money on a superb Vishera FX-8350 OCd to 4.5GHz guarenteeing no "bottlenecks" in the future. Update: If you are staying at single 1080p don't waste your money on CF.