Look at the treads to see the condition theyre in. If anything you might only need to hand scuff them with 100g or 120. Then for finish use a water borne urethane. First a sealer then 2 finish coats Before you apply the sealer wipe down the tread with denatured alcohol. This will help remove the surface oils.

A dark jatoba or espresso stain will take BC to a chocolate color. Do you know what flooring you have? If engineered with a thin veneer, proceed with caution. And obviously you're doing this for a potential buyer, so you might just want to offer them a credit on the purchase price and let the buyer deal with the refinishing of the floors. You never know if they'll balk at the new color or back out of the deal, etc. Mongo

I was originally going with Bellawood Bloodwood in my kitchen, which will have Bordeux stain on cherry cabinets. Seeing it all together made me change my mind because it was very dark, especially with Uba Tuba or Verde Butterfly granite. I'm keeping the cabinets and granite and going with tile instead. The Bloodwood is a darker, much redder hw than BC, but you might want to get samples of all of them and see what you think. I ordered one small cabinet door in my stain and got a fairly big sample piece of my granite, took it to Lumber Liqudators and put it up against the Bloodwood square that they had laid in their floor. I knew immediately it was too much dark. We are keeping the Bloodwood in the rest of the house, except for the laundry and bathrooms, but I liked the contrast of the light tile against the cabinets and granite better.

Since you do not want extremely dark floors, I would not stain the floors since the yellow orange color will dramatically get darker and richer and so will all the colors on the floor. I feel the floor will be richer and more beautiful and dark enough. Now if you told us you wanted very dark floors, then I would say stain them and they may get even darker. It is whatever you find beautiful. I really love the colors of Brazilian Cherry and that is why despite the darkening and color change under my furniture, it is what I have been wanting. I can't help you with finishing the floor since I never finished a floor before but I like semi-gloss and satin finishes on darker floors since high gloss on dark wood seems to show every drop of dust but that is just my opinion. Semi-gloss is my favorite finish on any hardwood floor.