Do you plan on crossfire in the future? If not get a 600 watt psu. Same with the mobo. IF you have no plans on cfx, you could get a $100 mobo that would be just as good for your needs. That ram looks fine to me. If it is more than $40 you are spending to much.
Yes, I'm planning to crossfire another 7950 in the near future.
Would all of it fit in the case?