What about unlaquered brass? You can keep it shiny gold if you want by regular polishing, or let it develop a darker patina (which it will do quickly in the bathroom). Then when if you get bored of the antique look, polish it again.

We actually could do antique brass, but unlaquered isn't an option with our builder. I wonder how to antique brass would look with the other gold fixtures.

The champagne gold would look really nice against the dark cabinet. It adds a nice, classy contrast.

I can't tell what I would be voting for. The answer is you should have more than one metal in a space. I recommend picking one metal for the "water" parts (the sink and shower faucets), and another HIGH CONTRASTING metal for the other parts (towel bars, toilet paper holder, and cabinetry). That way you have enough balance of like things vs. different things spread across the bathroom but also somewhat grouped together so that it doesn't look like a mish mash of randomness, and it is very clear that you are purposely not trying to match them. If your shower faucet is already champagne, then get matching sink faucets. Then I would do the rest in ORB, and to me that works because I like it when dark cabinetry has dark hardware in bathrooms so there isn't a high contrast in colors. There is no reason IMO for your eye to be drawn to the hardware in a bathroom (unlike when I want it to in others spaces, like a kitchen for example). So I like it when the hardware just blends in and disappears when it doesn't need to be singled out.