Darius, congrats on your decision. I've been listening to my M22s for about 6 1/2 years now and still no "fatigue", regardless of the length of the listening session. Your 605 has plenty of power capacity for your room and there's no need to look for more.

Very few comparisons in audio actually would justify terminology such as "night-and-day", "huge", "blows away", etc., although we see it used fairly often. Your M22s will be excellent; enjoy.

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Enjoy the music, not the equipment.