I beg to differ (as many other) that plugs/outlets cannot be used for tone controls.
As far as plating, gold is not really neutral. It's more warm sounding with rolled off highs. Rhodium is definitely more revealing, but probably more neutral. Silver plating is bright/fast and will push upper mids/highs. If you want true neutral, probably the best is nickel plating, but that is also lower quality and typically uses brass conductors (which in my opinion push the voltage too hard and sound becomes shouty).
Like other said, if budget is concern, the Porter Ports are cryo-treated hubbels.
Or get a PS Audio Power Port. They are nickel plated over copper. Probably the most neutral outlet, and only $49.