If it were me I'd use ss urethane and then clearcoat it.
Urethane is just as strong as clearcoat, they're both urethane.
Single stage urethane, especially black, has a deeper richer color.
Spray it black and clearcoat it, wait a day or two and sand it all smooth
with 600 grit then spray a couple more wet clear coats (a flowcoat)
That will give you a finish that looks buffed out without the buffing.
I've done it that way and it's amazing how much better the flowcoat
always lays down. If done right, it'll be slick as glass.