Remember guys, he is trying to wire a PAIR of dash speakers AND a PAIR of door speakers to one 2 channel amp.
The wiring I described above will give hime an 8ohm stereo load.
He could wire the speakers in parallel and get a 2ohm stereo load, but it sounds like it is wired this way now and he does not like it.
Also note, when you wire two speakers of differing impeadance to the same amp channel (ie...8ohm and 4ohm), the 4ohm speaker will play twice as loud and move twice as fast. This would not cause a problem in this case, but if you were to wire an 8ohm sub and a 4ohm sub parallel, that were sharing the same air space, you would get some bass cancellation at best and perhaps even destroy the speakers.
Been in car audio since 1988