Power Supply Question

I'm looking at Pc Power and Cooling's PSU. Sweet. They have great amperage ratings and their filtering, regulation, etc. is top notch. The only downside is that they are a little on the expensive side.
I want to know if all this ripple, voltage regulation, and filtering has anything to do with the DC power from the PSU to the computer components or does all this stuff just clean up the AC current from the outlet? This might not make sense but here's my reasoning. If all that the filtering/regulating components of the PSU do is clean up the AC current, why not get a good Line filter from APC or Triplite and then you can get a massive 500-600 watt PSU.
That way you could get more power and line filtering for around the same price. Or should I just get the PC Power Cooling PSU? Or should I save up my money and buy both the expensive PSU and a line Filter? What do you guys/gals think?

Sincerely,
Orangepiel7