Why Rhodium?

I have never really got on with Rhodium plugs myself although I understand the properties are useful (durable/resistance of oxidation etc).

I think Cpk has it right and it is the wire connecting between that is as important. I think you should try to stick to the same metal through the chain as much as you can.

While I have furutech plugs, in my set up the Oyaide plugs seem to have the edge. A little more solid through the mid and bass.

I use gold over copper (Furutech F1 25 gold series/Oyaide P079/C079) as it seems to let a little more richness through.

Some may consider Rhodium an, "excellent" conductor of electricity, but- to what are they comparing it? Silver's conductivity is 106, Gold's- 65 and platinum is 15 on the Electrical Conductivity chart(copper is considered the reference at 100). Rhodium(rated at 38) is better than platinum, but not as good as gold. It's attributes are durability and finish. Rhodium or Cardas? Personally: No- thank you. The better the conductivity of the material in question; the more transparent it will be. That means you will hear more of what your source(or whatever is upstream) is delivering(good OR bad).

Yeah, but the red, hot stamped Rhodium...
I'm waiting for the Cobalt.

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.

ANY time 2 different metals come into contact you form what is called a junction. It is called a thermocouple and produces a (minute amount) electrical current. While I wouldn't expect it to be a factor in power or power supply, it could be a large fraction of low voltage circuits, like phono.
This effect, (thermoelectric effect) should drive those nuts who can hear which way a fuse is installed in a power supply.
Rhodium is used in such couples, for many of the properties listed above.

Don't believe me? Get out a steel coat hanger and a piece of #12 copper wire.
Twist the ends firmly together. Use a vice and pliers if you have to. Connect the free ends to a DVM (what? You don't have a DVM? Shame!) and stick a match under the junction. You should get a couple MV, at least.