2 things you can do for low cost to improve your monitors sound.
1. Very cheap-go to Walmart and buy some "Pink Pearl" erasers (6 for 2 bucks) place 1 under each corner of the speakers (8 total) you will hear a difference total investment $4.00. (You have nothing to loose here-try it!)
2. Buy a furman power conditioner and plug your monitors in, you now also have an on/off switch, if yours were on the back, you will hear the difference, ebay price 60-100.00.
Now these are not earth shaking differences but for the $$ invested and if you have good ears you will hear it.