imaninatural
You have received a lot of good advice , but I'll still add my 2 cents worth .
Start with finding everything that is on the circuit that your system is on , then you should at least replace the outlet (s) that your system is on with a minimum of hospital grade ones , then open up every outlet , light switch and light fixture !! yes that's is a lot of work but I'll guess that there are loose wires somewhere . As you inspect the outlets and switches you can decide if you want to spend the money on replacing them with HG ones ( I did ) .
You could also do a quick test , take an extension cord of at least 12awg that is long enough to run your system to another outlet on another breaker circuit , just to see if the problem is your circuit or possibly even your system ( least likely ) .
If the problem of dimming light disappears then you can experiment with spending money power cords , more expensive outlets and even going to a dedicated line .
Good Luck