Will this PSU just be a load of crap for my needs?

I'm currently considering buying the Gigabyte ODIN GT 800W since my last PSU burn itself up (I think the fan failed...) I've just had a look and it says that the 3.5V and 5V rails supply only 150 watts... I also hear that this is what you supply a graphics card with... The problem then lies in the fact that my video card is a very power-hungry old beast and its peak consumption is around 450W... Is there some way I can adjust the output or something? Or is it best to just look for another PSU? I really don't know much about PSUs, I'm afraid...