i have 6 380s and 2 290x.  i love my 290x but they are so hot and loud.  plus take a lot of power.    One rig has a 270x and 3 380s.  73.5mh/sec 800 watts  my two 290x are underclocked, undervolted (26mh/sec each) and still run 84C at a very loud 65% fan speed.  My PCS 380x does 20.5mh/sec and you cant even hear the computer running. 72C

Also i game while i mine.  my 290x loses 4mh/sec while gaming, i still get 95FPS.  Just tried that on a 2gb 380.  FPS stutters averaged around 50 but didnt feel like it.  lost 16mh/sec