Zero -
I hope you won't be offended by a little advice born of 2 years experience with Henry's critters.
I have the Fire, and H2O monos. I can say this without flinching, what you put through these two amplifying units is what you hear. Although I could find very little on your Arcam. there may be a problem. I have had yet an over sampling CDP that didn't sound contrived. The highs always seemed forced, and astringent. Maybe your unit will fare better.
Your power cords are iffy. Zu calls them, self shielding. Outside speaker cables, class D owners have found up-grade power cords make the most difference, and the difference is not small. Again, they just may have the requisite shielding.
I doubt the conventional Monarch amps will have the clarity where you can hear upstream defects. I haven't heard a conventional amp that does. When I was running Pass Labs X-600 amps, I couldn't tell the difference between power cords, and CDPs were a matter of taste.
I preferred my non-oversampling Audio-Note DAC over other CDPs, but it didn't occur to me how necessary it would become when I bought Henry's amps and preamp. Through lots of trials, I found speaker leads should be bare, ultra thin and wide.
I commonly hear, "Class D is in it's infancy." Quite to the contrary, it is our understanding on how to get the best out of class D that is in it's infancy.