The amps were good; loud and clean. They have a cult following these days, and Andy Fuchs does some killer rebuilds with these. Unfortunately, though the amps were good, their cabs were less than stellar. They have a rep for developing plywood rattles.
The late 60's/early 70's had a bunch of guys jumping in the water; a few got the gold (Randall Smith (Mesa), Cliff Cooper (Orange) ), but most got peed on.
Plush was cloning Peavey and Fender, but they had outrageous tuck & roll. Looked great, sounded pretty cool.
Earth Sound Research was the Peavey cloning machine, I believe at that point with Earth, they were a flimsy pcb build. Now I gotta go find an Elk amp...