30A on a single 12V rail isn't very much for a 620W PSU...
The Corsair VX550 is 'only' 550W, but delivers 41A over a single 12V rail. Heck, even the VX450 (450W) delivers more than the Seventeam (33A, single 12V rail).
A relatively low 12V rail often reveals an old(er) design which is more generous toward the 3.3V and 5V rails. Thus, not the best pick for a modern PC.
I'd really check if you can find a Corsair VX550... it seems to be the unit for you.
I checked.... the Seventeam actually delivers 48A on a dual 12V rails (one of 18A, and one of 30A, and yes in this case they do add up, which is a RARE exception!)
The specs of the seventeam aren't bad at all...Edited by Chozart - 5/15/08 at 12:49pm