Hi, Craig. Something isn't quite matching up. Right next to me is an oak plywood bookcase finished with Minwax Golden Oak. It is almost a perfect match for the Natural in the Minwax color chart. The moldings around the bottom of the bookcase are solid oak and somewhat darker than the oak plywood but not as dark as the Golden Oak in the color chart. This is to be expected as 1.) plywood does not absorb stain as much as solid wood and 2.)Minwax stains never come out as dark as the color samples.
My guess is that your floor and stairs were actually done with the same stain. At this point, changing either would be a difficult proposition. Going to a lighter stain can be done either by stripping, bleaching and restaining or sanding all the finish off and refinishing. I would advise against stripping and bleaching as the process can be somewhat variable. With no comparable to test results, you will not be able to tell if you can change either stain to match exactly. Therefore, I would really suggest that you contact a pro with a lot of experience in color matching stains to give you some direction. You could end up doing a lot of work and end up with no real change otherwise.