The detailed information and feedback is much appreciated.
Why does the Heresy IV have two sets of binding posts? If the reason is multi-amping, why not three pairs? If the reason is biamping, it seems the use of the internal crossover network is assumed, with separate external power sources being used - one for the woofer, and the other for the midrange/tweeter combo. Is this worth the effort and expense?
We know that the internal crossover network of the Heresy IV splits the signal at ~850 hz. If I'm going to biamp, why not use an external crossover to split the signal at this frequency? Then I wouldn't be sending full range signal to both pairs of binding posts. 20-850 hz from one amp, 850 and above from the other. Perhaps this is simply a waste of time.
Not using both pairs of posts makes me feel like I'm leaving something unused, something that might improve... something.
BTW, my biamp setup worked fine, but either the Ashly crossover or the Fosi class D amp created occasional loud tones in one channel, so I'm dropping back to one amp (Schiit Aegir), which sounded great all along. I may try a Minidsp 2x4 HD /mic/REW combo to EQ the sound (because I can't seem to leave well enough alone.)