I've been using the GTX (R) and (G) for a while. I had all GTX outlets installed in the PS Audio P10 I just sold.
It should be noted that plating metals play an important role in the profile of your sound; this is true with outlets, power connectors, speaker cable connectors, etc. Gold has a warm, full-bodied sound, while Rhodium transmits less midrange, giving a leaner, faster, more neutral presentation.
Someone mentioned using Rhodium for tube gear (tubes can sometimes use an injection of speed). Your mains outlet should reflect the sound profile you're going for with your entire system and your power connectors for the component.