I'm sure that you can't go wrong with either the Synergistic Research powercell or the comparable Audioquest series conditioners. I have always liked the SR PowerCells. Very analog, natural sounding improvements all down your system.
The newer the model, the better the performance of course. They come with a high grade cable and new they will include one of their wonderful duplexes.
I have not heard the AQ conditioners, but they are also a creative, innovative company that really knows what they are doing. I like to buy something that has good resale potential, but mostly from a known company.
If you are a skilled listener, you would be bowled over by their purple duplex or fuse, or even more fantastic, the Master Fuse. If your system is revealing and you know what to listen for, these SR components are absolutely top notch.