I listened to a pair of Audio Research Reference 330Ms

I finally got a chance to listen to these amps.  I've waited 3 years to hear these things.  Here are my thoughts.

First of all the fit, finish, form and fancy of these amps is really impressive. It's an elegant design. They feel massive and substantial. They feel luxurious. 

The first thing I noticed is that they threw off very little heat. I assumed that KT 170 tubes would blaze with heat- like the 6550s in my ARC amp at home do. Wrong. These tubes are not wound up tight. They feel more like they are idling. 

As for the sound- mids, highs, details, depth, breadth are what you'd expect from a $90,000 set of amps. Exceptional and satisfying. But not much better than the Burmester 909 Mk 5. Maybe just as good. Not worse though. 

IMO ALL ARC tube gear has the same "voice". Warmly analytical but not a warm bubble bath (with somewhat grey water) like, say  the McIntosh MC 9011.

Where the amps made me smile was the slam bass. No flab, no mud, no exhausted bass extension. Not tube-y.  They are LOUD. Surprisingly so. Loud like a 1000 watt Bryston SS Monoblock is loud.  Surprisingly driving the Magico M7s at background music level there were layers of detail and wonderful bass.

Are they worth the ask? I have a pair on order. Definitely outside my budget but I suspect that long after the price is forgotten the quality and  sonic purity will continue to reward me. 

Bravo! ARC! You have outdone yourselves with this one.