To Aron Garrecht,
I read your excellent review of the Bel Canto REF150S and agree with it 100 percent, as I have one of these in my system. I was thinking of getting another for my second home.
You alluded to the REF500S. Do you think the REF500S is that much better than the REF150S if one doesn't plan to drive large speakers hard?
In comparing the REF150S to the REF500S, I'd have to say that there are more similarities than differences. The most noticeable difference I heard, other than an increase in power and dynamic headroom, was the added control and articulation in the bottom end. I remember low frequencies sounding more resolved and a bit more authoritative overall. The differences in the midrange and higher frequencies were subtle at best. If you are running efficient speakers, say, 89dB or better, and don't run them at really high volume levels, I think you can easily get away with going with the REF150S. I remember that amp sounding more powerful than its specifications would suggest.
That said, if your speakers require a bit more power to drive them properly, or you crave arresting dynamic swings partnered with improved control in the bottom end, you may want to explore the REF500S. My recommendation to you is to see if your dealer will let you take home a REF500S so that you can do a direct A/B comparison in your system, driving your speakers, in your room.
I hope this helps, and let me know which way you decide to go. . . . Aron Garrecht