It might be nice to try and match the color to the other piece you already have.

Well, I see dark blue on sideboard, pearly white on chairs and brown wood flooring. So that means better stay close to one of these existing colors. I wonder if you could switch the bookcase with the sideboard? That might change the way you look at your colorings. With the gold sofa I think I would do the bookcase in black. The chairs would look better with black and a black and gold throw over the arm and back of sofa would help tie things together. I will be back later with examples. Definite remove top overhanging cap if possible. Bbl

Have you considered using in another room, and repurposing it? Look at this!

I love this idea! A dust free shoe cabinet!! That would be very cool.

I tried to do a little mock up moving the bookcase painted black to the wall where your buffet is now and simulating the buffet with some art. I couldn't move the chairs, but the chairs would fit better with the bookcase on that wall if you leave both pieces in your room.

Had to just try blocking out your other pieces to this is far from perfect. But I do think the bookcase on that wall would look better if the buffet fits on the entry wall. Is that an entry wall where the lawyer bookcase is now? A large tall piece when entering a room is foreboding. If it isn't an entry area, then disregard. But since I only have this photo, just guessing. If you did paint the bookcase a black, I would also darken the blue on the buffet a bit.

For your sofa. Along with a black throw on the sofa would tie things together.

The buffet is about 2' too wide for the other wall

A dark slate grey with blue undertones would look similar to the other piece without being matchy matchy. I like the dimensionality of the cornice which, to my eye, gives the piece an architectural salvage vibe.

For my tastes, painting the white chairs a soft grey would make them look less stark and would enhance a monochromatic feel of using different shades of the same color (like a paint card). But always follow your tastes. If you like high contrast by all means design everything to your own aesthetic preferences.

Could you post photos from the other side of room and this piece? Give us more perspective on the room.

In any case, painting that piece will reduce its value, so think about that. It is a great piece.