I think ARC is doing more than upgrading capacitors. I loved my ARC 40th and switched to the Ref. 10. More than an icremental improvement: attact, bass, extension, mids, depth and width of sound stage, etc. Takes more than a capacitor tweek to deliver that. Don't get me wrong. The earlier ARC stuff is great. I just find the newer stuff alot better and so it should be with technolgy and if its going to go head-to-head with the top three, including Constellation.
Audio Research Reference 6 Preamp Review