The Minwax Helmsman spar urethane finish I put on my sansui 3000 cabinet turned out nicely. Incredibly durable. I don't know how many times I accidentally bumped the receiver but there are still no scratches or dings. You can get it in a can and use a brush to apply it, or spray can. Personally I would use a nice soft fine bristle brush and apply 2 or thre coats, sanding between each. You can get it at about any hardware place.
My thread is
here
The finished cabinet:
