Sansui80 - I have a Ref 2.2 (not Linear, but original) on which QFS did the "factory" upgrade. I am very pleased with the improvements - improved mid-range, smoother, more detailed yet less harsh. However, I've been told that QFS is no longer the U.S. distributor. I've also been told that the mod on the Ref 2.2 (replace output caps to 2.2 450 volt Auricaps precision caps, replace output diode, re-wire power supply for voltage to caps, replace output tube with JJ Tesla EC-99) is not really a good idea since tubes like the JJ Tesla EC-99 are not meant to be installed on their side, which is how the mod is done. I e-mailed Stephen Monte at QFS for clarification on this but got no response. So while I would highly recommend Stephen's mods for improved performance, I would be concerned about their application to the player. I have NEVER had any trouble with mine since (2 years now) but would be cautious since Stephen has not answered my conerns.