I think that the EQ can be ditched. Regardless of the hook-ups, (and I'm not going to dismantle it to see what they are), it's not necessary.
Because he has the 4 channel amp sending the Rio sound (since it is unpowered), to 4 speakers, the system must switch between "amp" and "non-amp" - the HU (self powered) is powering all 6 speakers (with all those rca jacks, I'm sure it can) when the rio is gone, or simply when the EQ is switched.
If I buy a HU with AUX-IN, I can plug the Rio into it, and use the HU rca out jacks to two amps, powering the front and rear speakers and a sub.
With the Rio plugged into the AUX-IN, all speakers should be powered, regardless of which unit is the source - no? Or do I need to use the Rio out jacks to it's own amp? I think that will be the final question. And getting 6 speaker/1 sub sound from each of them is the challenge, but getting clearer...
And either way, the eq is no longer a necessary evil. Switching sources and losing speakers. What a getto set-up I have now. I can't wait to fix this.
And I can see where the "eclipse" confusion came from - I am one confusing fella sometimes. Not intentionally, I assure you.