What is best is to take the factory amp and throw it in a dumpster, then put in a real amp and SINGLE COIL speakers with about number 12 wire running from amp to speaker (the factory wiring is silly for anything over 20 watts or to play music).

My SE is a base model, so it came with no rear speakers and no amp. I put in an 80 watt JVC head and Kenwood single coil speakers in back (Using factory mounts from a wrecked limited), then ran number 12 wire to the speakers. If I were to do it over again, I'd NOT use the factory mounts and put the rears in surface-mounted (that is, facing forward like a NORMAL installation). Mary Diaz in Georgia has her coupe done this way, sounds AWESOME.

I'd experiment with your ideas about how to wire them, and report back here - I've been here 12 years, I know of no one who has bothered to do the tests you speak of about trying various techniques in wiring the dual-coil speakers. (Actually, no, I'd not experiment, I do what I said, spend another $80-150 on an amp and run new wires to the back - that factory amp, like the factory head, dates back to the 1990s - and it is not very powerful at all. Putting new speakers in and wiring to that amp is like putting new tires on a car whose engine is running on two cylinders.)