Audioguru, I agree with your specs, but the addition of the YT2 and 2 diodes makes the output a Class AB output with active pull-down.
45Vdc with 5V drop on both bipolar (Darlington) drivers with 1.5A limit but using D²PAK RthJC = 3 °C/W which would require aggressive forced air cooling to dump 20W while delivering 30W at 60% efficiency to stay under 90'C,
Speaker impedance was not mentioned but it would be much higher than 8 Ohms. (60?)
But it should do 5W pretty easily. Class D is the way to go forward however. But this is cheap and dirty.