The overwhelming majority of wire in audio components is made from copper. In a perfect world you would have continuous copper wire with no connections or switches so the question becomes how to provide the best continuity/conductivity across the necessary connections. For example, I had an amplifier upgraded/rebuilt by SMc Audio and we decided to provide a captive power cord resulting in one less IEC connection. An audiophile could take that one step further and create a better connection to the wall by removing their $300 Furutech wall outlet and simply connecting their power cord by twisting it to the Romex and using two wire nuts (not recommended and not approved by code!). As other examples, it is not unusual for low current draw front end components to have no power switch, and I have heard of people removing speaker binding posts and soldering their speaker cables directly to the connector wires inside of their speakers.
To your question on sonic benefits resulting from different types of plating, I have not heard them. My amplifiers use Cardas unplated copper binding posts, which I clean occasionally (a couple of times a year) along with cleaning and reseating the spade connectors I use. I have used Cardas unplated copper spade connectors as well as Furutech spade connectors (which only come in gold or rhodium plate over copper). I have not heard a difference. FWIW, gold is a better conductor than rhodium (76% vs. 39% of the IACS conductivity of copper, which is 100%). Those platings are used primarily for corrosion control, but also as a sales incentive and, in some cases, to mask the use of inferior base metals. If you want the best conductivity as well as resistance to corrosion, find silver plated copper connectors since silver is 106% of IACS.
Interestingly, tin is only 15% of IACS but was/is used as a corrosion control on a lot of electrical connectors, which gets back to the original question, can you hear it? SUPRA uses tin-plated copper conductors in their Classic line (similar to Western Electric wire) as sort of a semiconductor (i.e., somewhere between a conductor and an insulator) and they state, "The tin plating improves sound quality by reducing the skin effect and the number of current jumps between the wire surfaces." I can attest that I do hear differences between the cables I have made using WE wire vs. unplated OFC or OCC copper wire - different but not universally better.
Back to your question, I believe that using a pure copper base metal is important but that the observable sonic impact of platings is probably small to none. However, take my comments with a grain of salt since I believe audiophiles are coerced into spending a lot of money to purchase a bunch of ancillary stuff that probably does little to nothing toward improving the sound of their systems.
