I'm no expert on this, but some friends of mine that made a living selling very high end HT equipment said that most of the line conditioners don't do much of anything, many of them can actually limit the amount of current your equipment can draw. The exception was Richard Gray's power company which uses massive inductors for line filtering, surge protection, etc. They have a "no risk" trial so you can take it home and if you don't see an improvement bring it back. I don't own one (yet).

-Jeff