It took me about a month to configure my Dennis Had Inspire SE amp (KT-150 w/ ~12 wpc) to sound 'right' with the Zu Omens. The bass was really woolly as supplied, and there was just no control in the lower registers - and seemingly very little power. For speakers with a sensitivity of 97 dB/W I was expecting to rattle the windows with 12 wpc.
After a few exchanges with Dennis via email, it became apparent that I needed to change the output taps from the transformer to a different impedance winding. This did require removing the bottom cover and resoldering a couple leads. I'm no stranger to a soldering iron, so this took all of about 2 minutes even for a relative novice. Since then, it's been a different world altogether. The power is thunderous and the bass is deep and solid. I just wanted to post this in case anyone ever ran into this down the road. With a 12 ohm speaker you need to change the output tap (or have Dennis do it to start with) to the high impedance tap for best results. He called the other tap the 9-16 ohm tap.