Hi Bself,
I used a Pioneer SX-1980 for a few years way back when. It was enormous (250 watts per channel at least) and weighed more than a 15 hp outboard motor I used on a utility boat.
Anyway, it should drive anything at 4 ohms or even less, although it is an example of an early solid-state design. It was one of the few solid-state amps of that era that could be driven into Transient Intermodulation Distortion (TIM), a phenomenon found in some of those early amps. It only exhibited this trait with one piano recording of Chopin, played very loud, that would send the input section of the SX1980 into a kind of oscillation that you'd hear from the tweeters. It was a kind of momentary raspy distortion on a sudden piano chord but it was quite audible with music. It was the only solid state amp I ever used that exhibited this liability.
TIM was discovered by a Finnish researcher named Matti Otala. Modern amps, so far as I know, don't have this problem. I've never heard it from any other amplifier.
Regards,
