Your PSU is certainly a bit small. If it is a goiod quality one you might just get away with it for now but it is debateable.
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 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 650W minimum.