TBH I can't decifer Katzer's voltage regulation graphs, apart from them all being in spec. But it shows ~50mV of ripple on all three main rails (+3.3, +5 & +12V), whereas the VP450 has ~70mV on the +12V rail and ~20mV on the +3.3 & +5V rail.
Hardware Secrets shows the VP450 with quite good voltage regulation and having fairly high peak efficiency.
Personally I think I would choose the Antec VP450.
The Enermax NAXN Basic 450W (ENP450AGT) is based on CWT's GPA design, which uses very poor quality capacitors (worse than those found in the VP-450 and SS-400ET), so I would recommend avoiding that.
The OCZ CoreXStream 500W hasn't been tested by a well known/reliable review site yet, as far as I know at least. It also looks to be a low end design, so it needs a positive review before it could be recommended.
I've already made the purchase.
I bought Antec VP550 just in case if I need extra power someday. It's really worth the money. It's really frightening to compare the old PSU with the Antec: the quality of the latter really stands out of the chinese crap I had before.
I did some overclocking for both the CPU and my new GPU (GE GTS 250). It's perfectly stable, in contrary to my previous power supply, which had just enough power, and even a little OC crashed the PC.