My HU now is an Eclipse (not the car, the car audio), so it's not factory. It has:
3 Pairs of RCA Pre-Amp Outputs
Non-Fading RCA Pre-Out Terminals for Subwoofer
2-Channel Selectable (IN/OUT) RCA Terminals for DSP Loop

But HU doesn't have aux line in. If I buy one that has all the same outputs/terminals as above AND AUX IN, can I listen to all 6 speakers? (given I am using a 4/3/2 channel amp) through both the Rio and the HU? I work in the ghetto, so driving to work I leave the Rio at home (see why I need the cd changer now?) and would still want full functionality of the HU (6 speaker sound & cd changer control)

How does this work if I want to drive a sub with the HU and Empeg too?

I think progress is being made. It sounds like no matter what, I can ditch the additional eq. Could be a situation of E-bay here I come, 1 casette deck and 1 eq for sale.

What do you all think now that I've provided some hopefully more helpful specs/alternatives?

Thanks. - Chris