I was selling those the year you bought yours!! I remember them well. That GM-H100 was the big dog of the group if I recall. I remember selling a whole boatload of the smaller variety GM-40's. Pioneer was very boastful of their power ratings. If I remember, the GM-40's were actually rated something like 17 watts/channel at 5% distortion!
Thanks for the feedback and the memories, but both my Kenwood Amps are about a decade older than yours. They are so old that they didn't even have RCA inputs on them!! Instead, there were specialty DIN cables that connected up with proprietary Kenwood head units of the era. I had to buy DIN to RCA converters for them way back when. Sure glad I did because I doubt they even make them anymore.
Pioneer, at the time I got my Kenwood stuff in the early 80's, also sold a line of amplifiers with a very weird proprietary connector. I was unable to find info in the vast internets, and my memory of the model numbers fail me. What I do remember is that the connector was a couple inches in diameter and once seated with a matching head unit was secured by screwing the two connectors together.
Adapters to convert these amplifiers to RCA input were made in later years (and they were expensive!!). We used to get a chuckle, even back in the early 90's (when I was still in retail audio) when somebody would come in with one of these troglodyte Pioneer amplifiers they bought at a pawn shop or garage sale for $20 looking for the adapters. When they were still available they were ridiculously expensive and people wanting to purchase them had no idea whether the amp they bought even worked or not! Few wanted to invest in such a gamble.
I'm still looking for somebody to top my ancient Kenwoods? Until then I'm King of the Antique Car Amps (OF THE WORLD!....bitches.)
This ain't no upwardly mobile freeway, this is the road to hell.