I sort of agree with Jeff. Many designers don't recommend power conditioners, however the high quality power supplies and circuits they build into their gear is in many regards a custom power condtioner. They have aready tweeked the power going in.
The power in my area, is decent but not the best, so I find conditioning a must. I have also become fan of some of the parallel filters on the market by Blue Circle, Richard Gray and Audio Prism. A parallel filter by being parallel is not in the way of the power flow. Some power cords do a nice job also. I have conditioners by Vanevers and Audio Power, as well as the Blue Circle and Audio Prism parallel filters in various spots.
Amplification aside, I find power conditioning a must for the best video performance in an HT system.