Try Bartley's Gel Stain. Two colors I would recommend are Pennsylvania Cherry and Dark Red Mahogany. They can go over minwax, and you can add as many coats as needed to get it dark.
Apply to one area or part at a time, and wipe to even out the tone. You have to work fast, don't go back over areas, and recoat after one day.
Casey

Another approach is to apply a coat or two of finish, then apply a glaze. You can use the gel stain as a glaze. I use glazes about 95% of the time I (re-)finish to adjust the color to get it just where I want it.

A glaze is simply a color applied between coats of finish, compared to a stain that is applied to bare wood.

Forget the finishing advice to use Polyshades. I also recommend you do not apply more coats of Minwax stain. It is not penetrating any more and can only cause problems such as not curing.

Here is a link that might be useful: glazing techniques