A friend of mine and I used both a stock and then Mini Lab Cable going into my Ultimate Outlet and then a Mini Lab going out to the CD player. We really couldn't tell a diffference between the cords on the input side of the UO, but there was a big difference on the output side of the UO.
To make matters even more confusing, there was a noticeable improvment when I upgraded from a Mini Lab cable to a Lab Cable for my PS Audio HCA-2 amp. These amps just sip juice and don't even get warm. Yet the huge Lab Cable made a big difference in the sound. I still want to get a P300 with multiwave for the source, but that's down the road.
BTW, my same friend had a Richard Gray in his system for a month or so, and it definitely helped. He also has a Power Wedge and it basically performs the same. I just preferred the UO. Taking them out of the system and plugging directly into the wall is almost torture now. Ditto, going back to stock power cords.