I am on the hunt for a tube pre amp for my classic cherry amp. I would like some pointers on how to pick a good match. I know that the input impediance and output impediance is important but I am not sure what the specs should be to match them up. Other than that is there any other specs I should pay attention to. By the way I am looking at a musica bella leanna vtps preamp on audiogon has anyone heard that before? thanks