Sometimes just power washing wood will brighten it again. You can buy power washers for a garden hose now that work really well. OR you can rent one for half a day or something.
I would NOT use a power washer on old dark wooden furniture! If there is any veneer-common in some old furniture--it would be ruined. A power washer is too powerful for old furniture finishes. Here are a few suggestions from a furniture refinisher: www.refinishwizard.com/cleaning_antique_furniture.html
I shall look at this website. My furniture is the old ball and claw and I do not want to ruin it.
The other pieces are even older
You could sand it down and stain it a lighter stain, paint it a light color such as white or a lighter brown. You could also strip it and bleach it with wood bleach! Hope this helps!
This looks doable for me. The stripper is less messy than sanding because I have to work indoors.
I agree with Gk, skip the power washer!