If you just want a PS for your present set up, a 550W will do, a 650W will give you some breathing room. If you plan to upgrade your graphics card in the future and even go CF/SLI then go with a nice 850W.
Coolermaster has a new set of power supplies out that are really neat. High efficiency so they run cool and quiet, plus modular cables to reduce cable clutter in your box to a minimum. Plus the cables are flat so they will route nicely and stay down.
I would just get that 7950 by powercolor if i was him.
you get 4 really cool games + it's like the best performance GPU for around 250$.
Personally though, i would suggest a GTX 770. Yes it's 150$ more expensive, yes you won't get any games.
But, wow it's performance should last you for another 3-4 years. the 7950 is already getting outdated with the latest most demanding games such as crisis 3.
I think in 3-4 years, 770 will still run games on high. But your 7950 will have to run games on medium-low, forcing you to make another big upgrade. In the long run, i think the 770 is cheaper, as i can just SLI another 770 as well for another 3-4 years of top tier performance. Crossfire just don't work that well as SLI