Yeah but that doesn't mean that the PSU can output the full 450 watts on the +12v rail, as a PSU should be able to do. It probably can (you're right 33 amps should be enough), but it's still be nice to see it.
I actually don't see in the specs anywhere that the power supply has any 6-pin connectors. You could use something like a molex-to-6 pin adapter, but the fact that it has no peripheral connectors is again worrying. I might be blind though.
Anyways the most power you could get out of a non auxiliary powered card would be a Radeon 7750, which only requires the power from the PCIe slot to function.
^ That's why most of my computers now are getting power supply replacements. I'm replacing TR2's and Dynex's I had for awhile with mostly Antec. I even replaced my main Ultra LSP in my main comptuer for an Antec (I didn't know about power supplies when I started building, now I do)
You can't compare the clocks of nVidia cards to AMD cards. Their shader cores and stream processing units are completely different architecturally. nVidia's shader cores are clocked a lot higher and do more work per clock cycle, but AMD utilizes a lot more stream processors. So the individual stats are apple and oranges, which is why benchmark results are used.