I recently took my Ref 75, which I had retubed with KT 150's, back to the dealer for upgrade to SE status. Fortunately, the distributor OK'd doing the SE upgrade without the cost of new ARC 150's. I was able to compare my Ref 75 with KT150's, with the dealers 75 SE. I can confirm that the SE upgrade to new capacitors etc, gave a similar increase in performance, to the KT 150 retubing. My original thought was most of the performance improvement was in the tubes, not the other changes in the SE upgrade. This, to my ears, appears not to be the case and you need the full SE upgrade package, to get all the benefit out of the 150 tubes.
