The 8-ohm taps are much more dynamics, better bass, well better everything, go to 4-ohm taps and sound is lifeless, easy to hear. My Dynaudio Confidence 5's I owned really came to life on the 4-ohm tap, 8 ohms defused sounding lacking real grunt in the bottom end, easy to tell which taps work, listen for dynamics and the bottom end detail and extension. I always try the different taps when I get new speakers, that the nice thing about having tube gear and McIntosh better solid-state amps that give you the choice of 2,4, and 8-ohm outs, you can really match your speakers to perfection amp wise. Also with the M3's depending on your floor and room, they can really sound better without the screw in spikes, just use the footers that come with the speaker, much more natural and deeper bass, more sweet highs, and a much better balance top to bottom, so make sure you try them both ways.