I do understand what you are saying, at least partially. I'm not sure where you got the hfe of 20. My spec sheet (Farichild 09/99) states a worst case hfe of 40 @ 500mA and shows a typical of around 80 @ 500ma. The transistor I am using actually measures at 121, but that is besides the point. Looking at DC characteristics in a circuit like this is pointless. The average current through the transistor is much less than 500ma. In fact, at 400hz the circuit only draws about 200ma.
I've come up with a 'better' circuit that will be (almost) idiot proof. I am just going to build it and test it to make sure it meets the design specs. However, I am cannot seem to come up with fool-proof design based on the simple switch we've been discussing here, so the new circuit is an AC-coupled class 'A'. I'll post the schematic when I'm done the tests.