I saw some info here on a tube buffer stage Gary Dodd is making now. Perhaps looking into it might solve your situation. he is also proposing a HP amp as well. The Dodd audio web site should inform you more. Both items run around a grand a piece, depending...
New MH PH25.2 Headphone Amp as tube buffer?
I see the new Music Hall PH25.2 Headphone Amplifier is a tube - solid state hybrid with a preamp output. Does this mean that the Music Hall can essentially function as a "tube buffer with potentiometer" for any source connected to the headphone amp's analog inputs and then routed via the MH's pre outputs to your standard line stage or integrated amp inputs? I am interested in trying a tube buffer for my solid state CD players and also a new headphone amp. Would this potentially work as both? Is it worth the trouble?