Thanks to all who gave advice. The router trammel worked perfectly to cut the curve. Several other things I did were less perfect, but should be instructive for the future.
Ergonomically, I can say that this is already a success. More desk room, less clutter, speakers and monitors at just the right height.
I finished it with four coats of Watco. Then, on a whim, I gave it a light sanding with 1000 grit paper and then paste wax. Soft luster and smooth as can be. I may try that again sometime.