Directionality in digital = impedance mismatch

This is my first post. It's great to participate given members' knowledge and experience. I have a little story to share which may encourage some feedback. My system is as follows:

* Amp: Manley 100W monoblocks (Svetlana winged C 6550 x 2)
* DACPRE: Monarchy M24 (Amperex Mullard 6DJ8 1976 A-frame x 4)
* Speakers: Harbeth SHL5 (special edition)
* Transport: Denon DCD-1500AE (SACD player)
* A/C: isolation transformer for sources
* Interconnects: Monster 400mk2 + Monster Coax digital (75 ohm)
* Speaker cable: OFC free generic copper cable (spades + bare)

David Manley is a very good friend, so he recommended most of the components above (apart from the Denon, which he said was rubbish). Nonetheless, the system is excellent and competes with others that cost much much more. Very involving and "foot-tapping".

Here's a funny story: after a few months of using the system, I discovered that my directional Monster coax (75 ohm) was connected in the wrong direction (arrow pointing to Denon). So i decided to "correct" the direction and reverse the cable (arrow pointing at DACPRE).

Result #1: timing of music "gone", foot-tapping disappeared, image became fuzzy, vocals move rather than center, and one of the Amperex 6DJ8 starts whistling and squealing at random intervals (with or without music).

Action: I blame the 6DJ8 and win two eBay auctions for Tesla and Amperex replacements. Then, after 2 frustrating days, it hits me (the damn coax cable). SO I REVERSE THE MONSTER COAX into the "wrong" direction (arrow pointing at Denon).

Result #2: MAGIC. The wrong coax cable direction makes everything "correct". Music gets back weight, timing, presence, etc... . Some may argue that this was caused because coax cable was "burnt-in" the wrong direction, hence, needs time to burn in correct direction. Seems that tube whistling has gone too.

Well I don't think so (apart from the die-electric theory). I blame the poor interfacing of equipment, especially mid-fi products such Denon. It seems it took two wrongs (wrong cable direction + bad Denon coax output) to reach a neutral state.

Morale of the story:

1. Mid-fi gear (i.e. Denon) is crap: I presume that the Denon does not have a decent coax interface, hence, must have either a coupling transformer (CC Poon) or reversed cable grounding to match impedance.

2. Mid-fi gear can ruin the rest of a high-end system through power interference and interface mismatches.

3. Buy a great transport (used) rather than new mid-fi transports. That's what Manley says anyway ("get the cheapest Meridian 2nd hand and you'll be fine")

4. With properly matched hi-fi gear, cable shouldn't matter. It seems cable only matters when there are electrical problems that need to be addressed.

Who shares these views, who thinks otherwise?

I don't see the need for exotic cable with properly matched components.