Without sounding rude i think peoples perception of what is smooth and whats not must vary wildly. I simply could not settle for a single 6950 so went crossfire to get the performance i want.
A single 6950 on ultra settings is not a pleasent expirience it sits around 30fps and fluctuates and is in no way smooth to play, it will play in all high settings at pretty much a solid 60fps no msaa.
If you want a single card solution that will last and you want it now then the 7950 is you only logical option.
Lomez i think you are missing the OP's main requirements of low noise and power consumption
Then again there are very few games that don't do well over 60FPS average maxed out at 1200p.
In fact it's really just BF3.