A 7850 needs a good 450w psu.
Here is a list of psu's sorted by quality tiers. Pick something in the tier 1-2 group.http://www.eggxpert.com/forums/thread/323050.aspx
If you live near a microcenter, they will sell you a 35770K for $190.
Intel 330 120gb SSD will sell for <$100.
It is considered more reliable.