I've looked around for a while, and my question appears to be very specific and I was hoping that someone who knew more about audio amplifiers could help.
I'm doing some research assistance where sound sources with impedances from 20-40 Ohms are going to need to be driven at 20W. Based on some Googling I've done, this appears to be very specialized. Even very expensive amplifiers are only rated with 4 to 8 Ohm load speakers. The amplifiers need to be suitable for audio (passband from maybe 100Hz to about 25kHz), and I've found nothing so far.
My question boils down to this: does anyone know where I might find such an amplifier, or whether I need to construct my own? I'd like to spend less than $100 on the amplifier, which may be impossible.