Hi - did find a review of Gig superb 550 on Hardware Secrets;
You should read it, here are some comments from the conclusions:
"We can't understand why when it comes to Power Supplies,
tier 1 Motherboard suppliers offer low end products"
"Superb 550 is a decent low end 450w unit if you pull between 180 and 270 w from it,
on other load patterns it's effeciency is too low"
"And to make things worse, we couldn't pull 550w from it"
"Superb 550 is far from superb, and too expensive for what it is"