Changing a speaker color

If the original paint is in good condition, it does not need to be stripped, only sanded to a matte finish. After removing all sanding dust, the original paint should function perfectly fine as a primer, assuming it had an automotive-grade finish to begin with. 

Remove the drivers and binding post plates prior to any of this of course, and mask off the holes. 

There is no way to achieve a true piano grade finish without a very controlled HVLP spray system/gun. I recommend that be handled by a professional, otherwise you’re likely to end up with runs, orange peel effect, or trapped debris.  
 

Vinyl wrap is a great idea if the cabinets are conducive to it. There are also products like 3M Dinoc that can produce a textured finish like faux carbon fiber (wouldn’t be my choice but it’s an option).