Why Rhodium?

I agree with Buconero. Rhodium plated connectors are, IMHO, a fad. Until recently Rhodium was cheaper than gold, and it does resist corrosion better than PURE silver plating. But it is not a preferred surface for wearing thrust contact conections. Mil-spec and industrial standards call specify gold as the preferred contact surface for gas tight cold contact electrical connections.

On top of that, you guys are kidding yourselves if you believe that the material used for the connector plating will have an enough effect on a signal to be audible, if even measurable.

Willoamp, industrial gold alloys do not oxidize and are considered extremely corrosion resistant. That's why gold is used for virtually all mil-spec and industrial purposes. There are a couple of limitations: 1) gold is not terribly wear resistant, so may not be the best choice for multiple mating cycles. 2) for cost purposes, some cable manufacturers use a thin gold wash rather than a properly prepared and applied gold plating. 3) gold plating can can be problematic if exposed to extreme thermal cycles if the plating surface has not been prepared properly.

Electrically, the best way to make cables is via a crimp connection using a die designed specifically for the cable and connector in question. What you want is what's called a gas-tight connection, and you can't get that via a screw collar. Solder joints are OK, but you need to clean the flux off of the conection carefully because it is hygroscopic and attracts water. Also, solder joins are somewhat fragile and can crck or break under the strain of multiple connections (mating cycles).

I still seriously doubt that anyone can hear the difference between any type of connector plating, unless you are running extremely high current through the lines. And even then...

Cpk, I have heard systems configured with all types of cables and connectors. IMHO with regard to interconnects, good connections (NOT connectors) matter most. The actual wire (assuming that you are within guidelines for inductance, capacitance and resistance) almost always do not matter.