Usually, the Tape 1 jacks are used for some kind of processor- Rec Our goes to the EQ's Input jacks and from the EQ's Output jacks to the Tape In jacks. If you were to connect the EQ's output to the power amp input, you wouldn't be able to control the volume because the Rec Out level is fixed.
Rat Shack never made (or had made for them) anything that was noteworthy. If you want a decent EQ from the '70s or '80s, look at the Pioneer 12 band models, Soundcraftsman, SAE or something like them. Audio Control came into the picture in the '80s, so don't eliminate them as a possibility. Most of them weren't particularly noise-free, so it's important to keep the level controls close to the unity gain area (+/- 0dB). Wide variations won't produce good sound and generally cause a lot of phase shift in these pieces, so if you want better sound rather than just buying a lot of older equipment, get an active equalizer. You would press/flip the Tape Monitor switch and leave it there when the EDQ is connected, then use the Tape Monitor switch on the EQ, with the tape deck connected to the jacks on the EQ instead of the ones on the integrated amp. Use the In/Out switch to use/bypass the EQ.
