The PSU is a bit heavy for a 7850.
If you could, I would aim for a 7870 XT. It's almost a 7950.http://pcpartpicker.com/parts/video-card/#c=124
A system with a 7850 requires about 500w, 600w if you CFX. Just to give you an idea of what you really need.
NOTE: Rosewill CAPSTONEs are fine, they are made by Super Flower, one of the few Rosewill PSU worth buying. Yours is a bit expensive though.