Sometimes obscenely high. In the mid-late 70s, there was a huge run up in (reported) amp power. Do a search on eBay for Marantz, and you'll see what I mean. 200 wpc and things of that sort.
Of course, my old Marantz was 20 wpc, so go fig. Same era. I had another one that was 52 wpc. And my big ol' Toshiba was something like 75 or 85.
Manuals? Yeah, got 'em. They're pretty much like manuals today, except printed on better paper and with real photos instead of line drawings. And less numbers in circles and squares and such.
I am the Doctor, and THIS... is my SPOON!