just to be clear, I recommended plugging into the wall to troubleshoot. I do believe in a quality power regenerator. but my regenerator costs 6X what your amp costs so in your price range, plugging into the wall is probably your best option. don't use a surge protector if you can avoid it. Better option is to unplug when lightning is in the area. Surge protectors don't always protect you or maybe usually don't protect you. but they give a lot of people peace of mind (perhaps undeservedly).
Also, as for a dedicated line, you may already have one. You have 3 outlets in the room you think are on the same circuit. open the breaker and see what else de-energizes. if there is nothing else on the circuit, then your noise level should be minimal. If there are outlets in another room, try not to use them. If there are lights, make sure they don't have a dimmer switch and keep them off when listening. If there are important items you can't do without that are making noise or pulling a lot of power, then you may need a dedicated line.
Jerry