Has anyone tried an amp from Class D Audio?

No, Spenceroo, I haven't. I will at some point, just want to break in the cables, etc, as I had to change cables once I bi-amped. I used to have Acoustic Zen Double Barrels, but now that I bi-amp I cant use them, so use Clear Day Double shotgun + Signal ultra, doubled up on each channel- each terminal has a banana and spade:)
Once everything is settled, I will switch the leads and will post my findings.

I have the SDS 470 driving the upper frequencies on a system biamped with Bel Canto 1000m reference on the bottom end and they sound fabulous. Speakers are SP Tech rev III, tube preamp EAR 868 .
Enthusiastically endorse the CDA as a bargain of the first order!