musical fidelity tube buffer

Given the level of your electronics, I personally would not want to run the risk of mucking it up with the (relatively) cheap (esp used) tube buffer. I'd think about selling the preamp and buying a tube one same brand/same price range.

First of all Mobile Fidelity does not make a tube buffer, but Musical Fidelity does. The purpose of the buffer is to present the driving component with a very high input impedance and the driven component with a low input impedance. The appropriate application for the product is when the driving component uses an inexpensive op amp output stage, think DVD players and cheap CD players here, or with very long cable runs that are adversely loading the driving component. Some also report a nice softness that the tube imparts in its distortion signature. I have one, but never use it with better components.

I think I am going to sell mine.