I just wanted to point out that I believe that there really is no difference of opinion here. Ryan has linked us to a thread where the OP is using a receiver and Denon CD player, probably the most appropriate use of this type of device as mass market CD players usually have OP amp output stages. I am sure that the buffer makes a good bit of difference in this application.
Later in the same thread a poster links us to his review on e-opinions and lists an inexpensive Sony CD player in his system.
Finally at the end of the thread, another poster reports good results with a Sherwood Newcastle receiver and a DVD player. This is the perfect application for a buffer, but whether the improvement comes from the fact that it is a buffer, which can be tube or solid state, or whether it is tube based is unknown.
I can report that in higher end, well balanced systems, the level of detail lost using my X-10D and X-PSU power supply is not worth any second harmonic glow added to the presentation IMHO.
