Can I plug a

PS Audio regenerator introduces extra source impedance which will limit current delivery capabilities necessary especially for poweramp. Bare in mind that in lots of components there are voltage regulators as well that will make them stable down to 100 V. 115V is sufficient enough and even 110V should not hurt. If Richard Grey pole able to keep 115V stable, it's where you want to be.

I don't like power conditioners, but found Richard Gray the very worst.

I was thinking of buying a PS Audio power regenarator and connecting that to the wall and then connecting the pole pig to that.

I would reverse the order - plug the RG Pole Pig into the wall & plug the AC regenerator to the Pole Pig. The quality of the AC from the wall has a big effect on the AC region - the Pole Pig can help to reduce the bad effects of AC from the wall outlet. This is what I do - I don't have the Pole Pig but I have 400S Mk1 & I have my PS Audio P300 connected to it the output of the 400S. Works great for me (i've only got the front-end components connected to the P300; electronics that draws 25W-50W i.e. low current). 

I don't like power conditioners, but found Richard Gray the very worst.

hmmmmm....very interesting stringreen. can you please elaborate why RGPS was the worst for you? thanks. 

So as long as it remains at 115 or above they are safe? My concern is the fluctuations. I read that the PS Audio keeps it steady at 120 without fluctuations. Is this true?

PS Audio's power plants appear to be similar to UPS battery backup units where they maintain 120V output regardless of the voltage at the receptacle. All you have to do is call them; they'll be more than happy to help.

Voltage fluctuations down to 112 volts is not necessarily a problem. While a ten volt drop may appear to be excessive, the equipment secondary voltage drop is a ratio of the primary/secondary voltage. If the equipment runs on, say, a 36 volt rail voltage, the voltage sag will only be 30% of the primary voltage sag. So an 8 volt drop at the wall outlet is seen as a 2.5 volt sag at the rail, which the regulators can handle with no problem whatsoever. For power amps with unregulated power supplies (which is most of them) a two or three volt drop will not affect performance as they have constant current sources on the supply rails to the gain stages. Those CCS's can easily maintain spec at that kind of varying voltage.