John,

You understand what's happening very clearly.

I wrote line level because that's what the sub's manual calls them. Yes, they are the speaker wires.

The 1080's binding posts are pretty big. I can stuff a couple 12 gauge wires under it if needed. Or better yet, I can solder two sets of wires onto a spade.

The gadget I'm looking to find does not appear to be made anymore.