The "100 watts" was probably "peak" (i.e., B.S.) power. As far as I recall Sanyo was never known for audiophile gear here in the US; strictly mass-market stuff sold in appliance and dept. stores. Not that the electronics were necessarily any the worse for that. You could probably ABX your unit's electronics with a good modern receiver and get a null (no difference) result as long as it wasn't pushed too hard. Trying it with up-to-date speakers sounds like a good idea!
As I have said ad nauseam elsewhere, I still have a 30+ year old Dynaco PAT-4 preamp and FM-5 tuner in my system! Yep, noisy pots, switches and all. My old Dyna Stereo 120 power amp gave up the ghost only about a year ago. I need to join the 21st century eventually.
I drive cars into the ground, too...