Getting power products right can be very difficult for many reasons. Its not like interconnects or speaker cables in the way you can get some consistant results from system to system. 2 people can have the same exact system but they will not have the same AC. Results are all over the place. Its just as easy to poor sound as it is to better your SQ.
In my opinion, there's only 1 way to do power products properly. You need to do an in home demo before you buy anything. I use The Cable Company (fatwyre.com). I don't know of any other place that can even come close to what they can do for you. Just call them up and tell them what you want to try, and a few days later you get a box with everything in it. They charge 5% of the total value of whatever they lend you. You can get the 5% back if buy something from them. It can be anything they sell, not just the stuff they lend you. The only expense you can't recover is shipping. I've been using them for years and can't say good about them. I wouldn't consider using anyone else.