I had recently changed my capacitors from white to red when one of the capacitors went bad on my REF 250s. ARC also replace the wire at that time and I later upgraded to KT 150. But did not hear much difference after all these changes.
Audio Research 75 SE
I just heard there is an Audio Research Ref 5 SE and they are offering the update to Ref 75 owners. Not only includes the 150 tube but also some circuit changes to better accommodate the new tube. Audio Research states this is a dramatic improvement as much so as from Ref 5 to the Ref 5SE.. Anybody heard it.