How to fight dirty power - I need your help

My system is AMC CD8B-Zucable Oxyfuel-CREEK-OHM12-Zucable Disco-Odyssey Stratos-Groneberg Quattro Reference-Migrage OM-10. My amp is directly plugged into a FIM outlet in the wall. The other component went through a Monster HTS2000. The voltage in my house is relatively high, usually in the range of 126-130V. The sound from my system is sometimes very good, but sometimes, especially in the evening, is tasteless. I believe the main reason is dirty power and high voltage. I’m trying to figure out an inexpensive way to fight the power problems. I don’t want to spend $1000-2000 to buy a power regulator. I’m thinking variac, but heard different opinions. I guess the result to some degree is system dependent. Now I need to figure out what is the key component that lowered sound quality when voltage is high or the power supply is dirty-CD player? Amp? What is the best way to solve the problem?