Home audio & video: setting up a sorround sound system using vintage stereo

Nice older piece of equipment but the crux of the matter is

that it only has two amplifier channels. It is possible to use that as two channels of extra power to add to another power source, but I wouldn't try to bother.

You need to start working on a new system. You can start off minimal & add on later like more speakers as budget allows.

Basically you need to past back with your realistic budget & spell out what you want to accomplish.