I recently bought a 500 watt PSU for next to no money (£11, less than $20). They're not as good, cheap ones, obviously, but I've only had one PSU die on me, and that why I've got my new one
. Cheap PSUs are a lot less likely to actually deliver their quoted wattage though, so I seriously doubt mine is actually a 500w PSU... it's not being pushed anywhere near that anyway, I just got it because it was cheap.
Back to your question.... 380watts should be fine to power your GFX (the 5700 isn't too power hungry IIRC), and almost certainly everything else, you don't say anything about the rest of your setup though.