I've put together a rig consisting of 4x 7950s in a milkcrate with powered risers running on BAMT r9 1.3 from USB drive. 1000w EVGA PS pulling 1100 at the wall.  This thing is currently keeping my garage above freezing but it is not as stable as i'd like. 

it seems to work great most of the time but occassionally i'll notice a card shuts down for no apparent reason, or my CPU usage pegs and the system is unresponsive. Last night I had 1 card that kept throttling back and reving its fan up as it was banging around 70c when the other cards were mid to low 60s. I can usually issue a coldreboot and it'll come back up and work fine for a while again. Sometimes after coldreboot it comes back up, i can ping it but no Remote Desktop availability. I have to Putty in and do another coldreboot or go physically reset the machine.

nothing is overclocked and BAMT seems to be adjusting voltage on the cards while running 2.2-2.3 Mh using the default config.  I'd like to get this thing stable then start tweaking the voltages down adjusting hashes/card... Is PS likely the problem? It seems to do alright so long as i just let it go but if i start trying to switch pools or am constantly monitoring the hashrates is when i notice issues.  BAMT r9 1.3