Improper ground


Okay, I've got a 20A circuit with 5 receptacles in the chain. Only one of the five have proper ground. As far as I can determine it's the first one in the chain (has a switch also, which btw when I turn it on/off a "pop" can be heard from my speakers). I have a 7 outlet power strip plugged into the grounded receptacle, which comforts me and where I plug my modest gear into since it's grounded.

All the receptacles in the circuit are getting exactly 123 volts each.

By plugging my amp straight into the improperly grounded outlet what are the risks here? Damage to the amp from normal every day usage (don't believe so). Should I get an electrician in here and ground the outlets.

I'm interested in whether I should be concerned with plugging my gear into non-grounded power socket(s)...
notec
Have you considered calling the manufacturer of your amplifier who would certainly be the most knowledgeable party about the specifics of your amplifier?
Your amp will be grounded when it is connected to the grounded source (via the I/C).
But... you want to be on the safe side, don't you? So, ask the manufacturer!
I would suggest that you do get a qualified electrician and have him check out the whole electrical system. Improper grounding could be an indication of other existing problems from poor connections to improper design. Safety is key, the amp can be replaced.
For $5 you can buy a 3 prong circuit tester, that way you can tell for sure what's grounded, determine proper phase etc.