I dont meant to bump this 3 month old thread up there but its relevant to the OP.
I have just done this little mod today with not much difficulty. I replaced the woofers with Alpine Type-s 3way speakers And going to use the woofer wires for a sub hook-up.
(I have pics but to lazy to upload at the moment but i will within the next day or so)
You have to remove the door panel to get to the speaker. the cover looks like it could come off but it doesnt, blah blah.
I spliced into the speaker harness and ran some speaker wire through the door into the cockpit, under the covers, behind the bolster and over the shock top mount and hooked up to the speaker. I also hooked up the door speaker back in just to test it out.
Results are that to "ME" the sound fills up the cabin quite nicely. Of course you are losing what we call the all BASS, but that is going to be filled in with a 12 jl in the near future. From listening to the 3ways it sounds so much cleaner and crisper than that of the door speaker itself. Of course. I will say that The highs and mids are ALOT better as well. I had to turn down the Treble to keep it within reason.
All i can say is that I like how it sounds, it sounds like my old car where it had full ranges in the rear deck(pushing the sound up and follows the roofline, rather than the door speakers where its heard from your feet up if you know what i mean)
all in all I like how it is and I cant wait to hook up my JL