I recently purchased the Monster 2500, not only is it a nice unit, but make sure you get it online to save about $100.00. It helped clean up some of the picture quality (Samsung DLP) and my audio (Harman Kardon with Klipsch speakers)is clear and clean. I definitely recommend it. Plus, they give a warranty for any surge damages.
I purchased the HTS3500 for my sustem. I have noticed more brighter tones coming out of my speakers. Much cleaner sound. Some people swear by the power conditioners others do not, they say its a waste of money. please read the following excerp & the comments by purchasing individuals. http://www.audiorevolution.com/equip/monsterhts3500/