Best Power Cord for REL Stadium III

In my experience, a rhodium plug/IEC should lean out the bass a bit. You could replace the plugs on your DIY cord with some of the inexpensive rhodium plugs on E-Bay. I have tried them and they are quite good.

Alternatively, you could pick up another cord. I use Kaplan cables and the rhodium version has tighter, less full, bass than the copper cord.

Just FYI, the plugs I bought don't say Oyaide anywhere on them. The construction of them is slightly different than a genuine Oyaide, so perhaps they might not sound as good as a real Oyaide. Also note there are no UL markings. However, they do sound very good. I can't advocate counterfeiting, but in the case where the items are not portended to be something they are not, I have no qualms.

IMO, at least this gives one an inexpensive way to test-sample a few different platings. Then, if so inclined, one can use that info to help with the selection of a more expensive, safety lab listed, plug.

Glad to hear you've made some progress. I appreciate you being open minded regarding these tweaks. In general, I've found gold plated plugs have full bass, and roll off or color the highs. Pure copper or brass have full bass, with the pure copper having cleaner mids and highs.

Rhodium gives more detail and smoothness, with tighter bass, but less layering of the soundstage as compared to pure copper. The end caps and termination types may come into play too, but I haven't really tested those out enough yet. At least that's what I hear. YMMV

Yeah, I would tend to think the FI-03 might help a bit.