I have an old (1980's) ARC Classic 60 that I'm using as a spare while awaiting my new REF-75. The tech I use went completely through the CL-60 ... and its sounding fantastic. Very musical and lush. Three dimensional as all get out too. But compared to the REF-75 with the KT-150 tubes I just sold, its no contest. The CL-60 is kind of a cross between classic tube gear (warm & lush) and more modern gear. If you like movies done in Technicolor, you'd like the CL-60. And hey ... who doesn't like Technicolor movies? Remember the original of The Wizard of Oz? The REF-75, on the other hand, transcends tubes and solid state and just gets out of the way of the music. The REF-75 comes closer to NO AMP than any amp I've had in my system. To me, the ARC advancements are clearly dramatic improvements over the years ... and I for one am happy to follow the upgrade path.