I'm building a new pc and have not done so in a while.  I'm looking at Antec's or Enermax's.  But i see PFC seems to be a possible good thing.  Any opinions or info on it?

Look at OCZ also, if you want quality that is.  Antecs and Enermax PSUs are okay, but dont even come remotely close to an OCZ.

Oh, and you want an Active PFC if you can get one, but its not that big of a deal, I wouldnt go to the end of the earth to find a good one.  

The difference is, if you dont know -

Passive PFC uses passive elements such as a ferrite core inductor on the input source to create a countering reactance. While easily applied to the existing power circuitry without much modification, the power factor is low (60 - 80%), the AC input must be chosen (115VAC / 230VAC), and the harmonics produced from the difference between the capacitance and the inductance are hard to control. Significant electromagnetic noise can result.

Active PFC uses switching regulator technology with active elements such as IC, FET and diodes, to create a PFC circuit This circuit has a theoretical power factor of over 95%, reduces total harmonics noticeably, and automatically adjusts for AC input voltage. However, it requires a complex EMI filter and an input source circuit, and is more costly to build.

are all the 12 volt ATX power supplies ATX 2?

I'm at newegg right now but I dont see 2.0 listed on many of them that seem like they should be.  

I know the dual 12 volt rails are susposed to be better for stable power for overclocking.  I'm looking for 450-500 watts, active pfc, and dual 12 volt rail and atx 2.  but I don't know how to tell if it is atx 2 or not.