How to clean the exterior of an amp?

Ordinary window cleaner with ammonia works well. Splurge for Windex!

To actually polish chromed or painted surfaces use a clearcoat-safe car wax like Meguiar's Cleaner/Wax. Avoid grit-bearing cleaners like Brasso and silver polish unless you're in a hurry to see the metal underneath the finish.

For the most stubborn rust spots or when all else fails use 0000 steel wool and chase it with a coat of wax.

If you rub so hard a genie appears, wish for a new component!

With an Accuphase C-200 that I got that is a bit grimy and dirty I tried using 91% Isopryl Alcohol on the front face and knobs. It did get the dirt out but there was a haze left over when I was cleaning. I would put the Alcohol onto a cotton pad and rub away. I might try some of the methods mentioned above. Anyone else have any hints on cleaning vintage gear?

Try some GooGone from Loew's or some other hardware store. It's citrus based and is great for all kinds of metal surfaces.

Use windex. On anything except newer Cambridge Audio.