I think combining both together would work best. Since your bed is so luxury looking, gold seems to fit with that style. But if you use all gold, then it's too much of the same thing. Adding ivory would bring some contrast (since also, gold and honey walnut wood look similar).

if the boxspring shows, i would try to get a sheet to cover it in a color that doesn't stand out so much...darker and closer to the wood color.
i don't think your mattress sheets necessarily need to match the boxspring cover tho.

So it sounds like covering the box spring with gold or some dark colored sheet, and the mattress with ivory sheet will work. Yay!

I could also get Taupe color sheet (in the attached link) for the box spring. Would that be a little better than gold?

Here is a link that might be useful: Solid Sheet Colors