[Bar81]

MX-R Twenty vs. M400:
Full disclosure: The dealer only had the original MX-R but in my experience the Twenty is an evolution of the original and I am quite familiar with what changed vis a vis the original since I've owned the original for years and the Twenties since the start of the year.

What really surprised me was the clear superiority of the M400 with a speaker like the Avalon Isis that the original MX-R drove amazingly well (in fact it was that combo that made me fall for the Isis - still an amazing speaker). The M400s exhibited an iron fist on the woofers, brought out more inner detail in voices and instruments and produced highs that were sublimely smooth.

On the tweeter, something very interesting occurred. I was always under the impression that the slight whitish tinge/slight piercing nature on cymbals, etc. in some recordings was a necessary evil of accurate reproduction on a metal tweeter. However, that doesn't seem to be the case. Those recordings exhibited the same whitish/piercing nature on Avalon's diamond tweeters. However, when we switched to the M400 that characteristic disappeared. Did the M400 roll off the highs? Not that I can detect but I can't be 100% sure.

The other characteristic of the M400 that I want to point out is that it is warmer than the MX-R Twenty - not by a large amount but it was noticeable. With a warmer speaker that might prove to be a little much if you're looking for anything close to accurate reproduction.

While I do feel that the M400 is clearly superior to the MX-R Twenty, my existing opinion of the MX-R Twenties remains unchanged - they are excellent and remain legitimate end game amps. For those not wanting to pay the ridiculous pricepoint of the D'Agostinos, not having a difficult speaker and/or with warm speakers, the MX-R Twenty could definitely be the right call.