Heres a quick leason in psus... No one seems to explain out things.
Your current psu is 550W &31Amps. Which is the right amount of Watts for your setup, but the Amps are low.
The raidmax is 630W and 2 22Amp lines, so not quite 40Amps total.
Now look at the Antec muffin posted. 520W and 40Amps. So, alittle less Watts than your powerup, and the same Amps as the raidmax, but the raidmax has 110Ws more power. From this you can see that the Antec puts out alot better power, and is reguarded as a better psu.
OCZ has some nice sales on right now, a 600W for 49.99, a 550W for 39.99 all with free shipping. Not sure vwhat your budget is, but if you want, give a price, and we can maximize your money.