Mike, Howard, All,
Thank you for your replies.
Mike: When I had the XA100.5 amps (also in a second story room), I would routinely get an increase of about 8 degrees in the first hour, peaking at about 10 degrees steady state. While this was less than your 12 degrees increase, you can see why I also had to sell them. I understand by definition of Class A one must deal with the inefficiencies of the design, but I was hoping somewhere down the line the laws of physics might be bent such than you could reap the Class A harvest without the drawbacks (perhaps the X.8 series).
It is interesting to hear you state that if you were buying today the XA60.8s would be on your list. Does this mean that to your ears you would prefer these to some of the units you currently have (particularly the D’Agostino amps)? I ask because prior to switching to the Momentums recently, I have been a dye-in-the-wool Pass guy since the late Threshold days. So, you absolutely don’t need to convince me that Mr. Pass is a world class designer that produces fantastic equipment. However, to my ears, I found the Momentums to be more to my liking across the board over the XA series. Of course, you might argue that is comparing apples to oranges (from a design and price pov) and that I should compare the Xs series (of which I have not yet heard). Given you have experience with both the X.8 and Momentums, I would be curious to hear your contrast of both designs. To my ears, I just found the Momentums to be more musical and enjoyable and they run cool as a cucumber to boot. This, again, is not meant to slight the Pass amps as they have a glorious midrange and served me well for many years.
If this is getting off topic for this thread, I apologize (sorry, still new to this board), I would be happy to take it offline or move to the proper thread with you (just let me know).
Anthony - like you said, the Momentum's are more to my liking as well. More liquid, with bass speed, punch and dynamics. What surprises me the most is the midrange bloom. Like you, I am very happy with the D'Agostino amp/preamp and if I had to only live with one amp/preamp, the D'Agostino would be it.
Regarding the XA.8 series, what I heard at CES was VERY good. Nelson & Co. are geniuses and when I think about their history, they really haven't ever made a "bad" product per se. All their products serve a particular need, with great value at a respective fair price point.
That being said, if I was looking to add to my stable of amps, the XA60.8's would be it.