This thread is almost 8 months old, but I would like to respond to gpgr4blu's last post. Gpgr4blu said that:
I moved from the Ref 150 to Ref 150 with KT 150s which ARC reps told me was almost as good as the Ref 150se. Then I moved up to Ref160 monos. There was a difference between my Ref 150 with KT150s and the Ref 160 monos but it was maybe 15 percent for twice the price. I assume the Ref 160s would be in the range of 10 to 12 percent better than your amp.
Obviously, unless one could do an A/B comparison of the Ref 150SE to the Ref 160 in one's own home on one's own gear, and after break-in, it is difficult to speculate how much better one amp will sound over the other in a shoot-out.
But FWIW, here's an experience I had with my Ref 150 amp that may have some bearing on gpgr4blu's comment. Some 5 or 6 years ago, I incrementally tweaked my Ref 150 amp. First, I swapped out the stock KT-120s for 3rd party vendor KT-150s. No question, there was a noticeable incremental improvement in SQ. Next, I sprung for the SE factory upgrade, which included ARC matched KT-150s.
If I recall, the SE upgrade included the replacement of a bunch of passives and maybe the power supply caps too. The SQ improvement was much more than "just incremental," ... it was significant.
So, ... going back to what gpgr4blu posted, I surmise that if I could do the Ref 150SE/Ref 160 shoot-out in my house and on my equipment, even if I stipulate that the Ref 160 sounds better than the Ref 150SE, ... I surmise the difference might be less than the 15% delta reported by gpgr4blu.
Reason: gpgr4blue compared the Ref 150 w/KT-150 tubes (but not the SE upgrade) to the Ref 160. Because, IMO, the SE upgrade effected a significant improvement in SQ, I surmise the improved Ref 150SE might nudge a little closer in SQ to the Ref 160.
IME, at some point in the OJ making process, a hard squeeze only yields a small amount of juice.
That said, I look forward to reading comments from folks who A/B'ed the Ref 150SE to the Ref 160 under controlled conditions.
BIF