Anyone refinished a plinth?

I've done a fair amount of veneer work as of late. I would be careful if you don't know what you are doing. It doesn't take much to sand through the veneer. Plus, to get all the top coat off so that you can apply a transparent black dye or similar, could be tricky. If you don't get remove it completely, you may have some areas that won't take dye (or stain) well. Then you'll have to apply a topcoat of your own. not saying it can't be done, but if you don't do this type of stuff regularly, I would think twice.

It really depends on what kind of result you are after. If you don't mind it looking like a DIY project, then maybe it would be a good learning experience and encourage you to try other things (like speaker building, etc. if you don't already do that)

If you are looking to stain it black, you should strip the finish, not sand it. Even then it may be blotchy. Painting it black would be safer, albeit a different look.

Completely agree with above responses. You're likely to either wear through the veneer if you sand or end up with a blotchy, uneven stain job if you strip. Paint is a better option if you want a predictable outcome. It's not impossible to do what you want to do, but it is a job that takes woodworking finesse.