When you come to upgrade the PSU make sure that you never buy a cheap and nasty power supply they can go wrong and take out all you other expensive components at the same time. Not only that just because it is marked 600W often they are nowhere near that rating. Purchase a good quality make like Seasonic, CWT, Corsair, Thermaltake, Enermax, Gigabyte, Coolermaster, Antec, etc and try and get one with a single 12V rail if possible. I would advise you to get one of about 750W minimum depending on your hardware demands and if you intend to run another graphics card in SLI or Crossfire then I wouldn't even look at anything below 850W.