Actually there's probably just one for tweeters and the 6.5s up front, and then the crossover is somewhere along the line in the factory wiring.
The easiest way to test for the right speakers is to unplug the output plug from the infinity amp, then use a speaker popper to figure out the speaker locations. Get a 9 volt battery and attatch some short test leads to the two terminals. Then pick a pair of wires from the infinity plug, and touch the positive lead from the 9v battery to one wire, and touch the negative lead to another wire. keep on doing this until you hear a popping or crackling sound coming from one of the speakers in the vehicle. Once that happens, you know the two wires are for a speaker, so then you'll want to test for correct polarity.
To find the correct polarity, you'll have to test each pair of wires for voltage. Instead of using the vehicle chassis for the negative/ground test lead, just pick the other speaker wire. If, with the system turned on, you get positive voltage, the factory wire touching the positive test lead is the positive speaker wire; if you get negative voltage, the factory wire touching the negative test lead is the positive speaker wire.
Once you've found a pair and gotten the polarity correct, you might as well label them or at least tape them off. And continue the process, starting with the speaker popper, for the rest of the wires, til you have tested all the wires.
One thing to note: make sure that you do the speaker popping on cable that plugs in to the the amp's OUTPUT connector, not the input connector. It'd probably be best to use a multimeter to figure out which harness/pins are getting constant 12 volts, switched 12 volts, remote turn-on, etc. If you do the speaker popper on the amp itself, or on the wires that go to its input connector, you might damage either the factory amp and/or the factory head unit.
Thanks for the detailed explanation. I'll give it a try this weekend. I appreciate the help.
-greg