What voltage can damage audio equipment?

Hi all, I'm hoping someone could help me out here about power requirements.

I have a Panamax M5100-EX power conditioner, which I connect most of my components to. My components are an Anthem AVM20 preamp, two Proceed AMP3 Power Amps, TV, CD player and a Marantz receiver (that I'm using to power my rear 2 channels in my 7.1 setup). I have everything connected to the Panamax except the Anthem, which is separately protected, but on the same outlet.

I have 200amp service coming into the house.

Basically, when I power my components on, the Panamax says 120v in the light indicators. Sometimes, this fluctuates between 120v and 115v. However, when I turn on the Marantz to power my rear channels, the Panamax blue indicator stays at 115v and will only occasionally go up to 120.

I'm not an electrician. So my questions are:

1) Will this dip or fluctuation damage my equipment??
2) What is a safe voltage range?
3) If this dip to 115v is bad then would a voltage regulator help?? I've seen some power conditioners claim that they are also voltage regulators.
4) If I'm experiencing a drain on the line, how can a voltage regulator maintain a consistent 120?
5) What other suggestions (preferably low cost, which means under $400-$500) might help if I do have an issue?

Again, I'm not an electrician, so I figured I'd ask the brain trust here :-)

Thanks!!
Theo