Any suggestions on Tube Buffers?

This is pretty funny actually. The purpose of a buffer is to compensate for incompatibility in impedances between components, the input impedance of a buffer being very high, and the output impedance being very low. I know that it is obvious, but that is why it is called a "buffer", not a makeyourhifisoundtubeywhatzit. It is a very useful device if the driving source has a higher output impedance such as inexpensive CD or DVD players that use op amp based output stages driving inputs of highish input impedance or long cable runs. Presumably, your preamp and amp are matched, so better sound does not come from adding a set of interconnects and an active device between them, a cheap active device, with a minimal power supply to boot. My best advice is to save for a nice tube preamp. They come up on Audiogon frequently starting around $300.00. If you like it, you will be able to sell your present preamp and recoup a substatial part of your investment and probably end up in a pretty similar place cost wise. And yes, I actually own a tube buffer, but do not use it. Just my two cents.

In the above post, it should say......"driving inputs of lowish input impedance", not highish input impedance. Of course.

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.