Lol, been shown not to have effects by whom? Are you seriously trying to argue that the entire high-end is essentially a scam, or waste of time, because most of what you pay for are components like better and better power supplies, more accurate clocks, better connectors, etc?
A question: have you actually listened to a component which has been reclocked, or had an upgraded PSU, etc, or are you just working from an inherited blind assumption that 'it can't work', without trying?
Another question: what does a PSU done properly mean? Surely you don't believe there is only one level of good or bad? Aren't there degrees, all of which demand slightly better, more expensive components, and techniques all of which are incrementally more costly? If this isn't the case, why is John Westlake himself, who designed the MDAC, have a PSU upgrade in the works, and a clock-locked transport, etc? By your argument this would mean either that he designed both badly to start with, or that he's on a scam of some sort selling upgrades which are proven to have no effect to unsuspecting, ignorant, punters. I believe neither, simply that he considers them important to incrementally optimise because most commercial products are built down to a price. Almost all the respected magazines include measurements of clock jitter and any PSU related distortions. The HiFi world technical report on the TeddyDAC said something along the lines that it had better PSU and sounded better as a result.
Are you questioning the reality of cable reflection in digital coaxial cable, or the fact that if a connector isn't 75ohm it'll cause an impedance mismatch which reflects the signal back?
The first query into google provided this about impedance mismatch causing reflections in cables:
Here's Van den Hul's explanation:
Here's an oscilloscope showing cable reflection:
This guy talks about impedance mismatch as it relates to reflection in red book transports:
Here's a trace showing a before/after attenuator minimising reflection due to impedance mismatch:
The best connector is an AES/EBU, but for single ended, a BNC connector rated at 75ohm is the best. AFAIK the WBT NextGen plugs and sockets are the only RCA type connectors to be a true 75ohm connector.