When I painted my subs I used all automotive finish's. High build primer then basecoat/ clearcoat. Its the only way to get that high gloss finish unless you have the time and patience to do a lacquer paint job which requires a ton of sanding painting and waiting . Even on the speakers I veneered I used automotive clear coat. As for the question about sanding the front. If you want a shiny clear coat smooth finish you need to sand as smooth as you can or it will take many coats of clear with sanding in between coats to get it level. Stain will cause the grain to swell and become uneven as well, i have never sanded after staining so you on your own there. The finish is the hardest part of the project by far. I am in the automotive sector so I have friends at the local parts store and I have picked up paint that was mixed incorrectly for free a few times but the rest I pay for myself and even with my discount it can easily top 300 bux. I tried the urethane from a hardware store and it just doesn't dry quick enough and spraying it is next to impossible .

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M80 V3 MY GLOSS Cherry