That would be great, would love a lesson on setting gains. Would also like some info on how to get this junk up and running. Normally I pay people to do this type of thing because I dislike it and prefer to spend my time on other things. Just trying to make an attempt at making this stuff work before I throw it all out. So in summary yes I do need a lesson in setting gains and filters, and wiring, and box building, and equipment know how, and everything else car audio related.
So with that out of the way, I disconnected the rear speakers from the amp and didn't see any improvement. Currently here is what is running: HU half volume - 4 channel amp front set only, gain set at 1/4 (just so that you have some baseline for which to view my inquiry) - Mono amp running off rear set of RCA from line out converter, gain set at 1/2 (just so that you have some baseline for which to view my inquiry). No bass boost. Low Pass set halfway. Subsonic filter set halfway. Remote knob set at full.
Front speakers operate as they should. When both the left and right RCAs are hooked to the mono amp the sub is muted. When one of the RCAs is removed the sub will perform as expected despite cricket chirping sounds.