I standby what I stated in the post Verdinut linked, unless and until someone prove my logic wrong, with facts, not hearsay/opinions. The fact is, those HDAMs are simply discrete (as opposed to ICs) op amps with unity gain. Unity gain means the amplification ratio is 1, that is, it doesn't amplify the signal, and it acts as a "buffer". Based on the positioning of the HDAM, that is, right at the end of the preamp/DAC signal chain, that is right before the power amp input, I would say it is 99.9% hype. It is simple logic, it is a buffer only so it won't change the sound characteristics except it would add a little more distortions and noise. It may offer higher slew rate by itself, but in that case the slew rate would be bottlenecked by the op amps and volume control ICs upstream, so that particular claim is pure BS. HDAMs in the Marantz integrated amps are more legit (in terms of their advertised benefits) because of the way they are applied, not not in the AVRs/AVPs. Case in point, the slim line series (probably also the NR series but have to double check first..) don't have HDAMs.
The 0.1% potential benefit would, or could be, in theory, improve the AVRs ability to drive power amps that have relatively low input impedance, but then based on bench test results it did not seem to even do that.