Ask the guys at Home Depot - they know their stuff and can explain it to you.

"Ask the guys at Home Depot - they know their stuff and can explain it to you."

Most barely know the products they are selling, and nothing about things not on their shelves.

Depending on what the existing finish is you may be able to screen it (very light sanding to roughen it slightly) and apply a compatible new finish over the existing finish.

I would think that a tinted polyurethane would scratch and wear off pretty quickly. I have heard of stripping the old finish before staining or re-finishing, but why not sand it so you have a more uniform surface to work with? You will get a better look if you do it the way the professionals do it. (Or, for that matter, hire a professional).

For a piece of lightly used furniture or vertical millwork, using a tinted topcoat or gelstain might be a possibility. (It will be more opaque and obscure the grain more than a traditional stain approach though.) Those types of areas don't get much wear/abuse. The problem with a tinted film forming finish is that it will wear off/scratch off and expose the lighter wood areas, and a floor is a heavy use area. If you want your floors a darker color, the traditional route of sanding the finish off completely and then restaining and recoating with a finish is the only way to go.

Tinted polyurethane can be used to darken the floor slightly. However, it will wear and where it wears the lighter color will reappear.

There may not be a good solution. Even if you remove the existing coatings, they have probably penetrated into the wood far enough to leave streaks and blotches if you try to re-stain to a darker color. In any event it is a job for a professional who can streak and color match with a brush if this proves necessary -- and it is probably going to be expensive. On the other hand if the stain does take well, the refinish should not be more than $2.00 s/f if you move the furniture.