Most of Radio Shack's audio equipment was rebranded stereo stuff from other manufacturers (some you'd probably be surprised at). Honestly, it was stuff they could get on surplus and charge a large markup on (on a lot of it, they simply changed the color of the bulbs and put their own brand name on it).
Same with their car stereos.
I worked there during the early '90's and remember that catalog. It was a year old when I started, but we kept it around as a reference.
As an ex-employee, I will tell you the place quickly turned into a nightmare to work at, and I don't miss it at all.
Some of you guys are romanticizing it. Trust me, it was a nightmare behind the scenes.