2001 Mitsubishi Montero, head unit

I have a friend that wants to put a new head unit in his 2001 Montero.  He was looking on Crutchfield.com for a head unit and he saw a notation that installing a new head unit would require him to run speaker wire from the head unit to each speaker, by-passing the factory amp.  Is this really the case? 

I only ask because I have a 2002 Sonata that has a factory amp and when I changed my head unit...I wired the speaker connections and the sound is going through the factory amp and sounds great.

Any feedback would be greatly appreciated, thanks.

Mike

If this is a seven speaker setup like the eclipse, it can be done easily enough using a tone generator, but you're best off running new wires.  Also, if this is a seven speaker system- I always disconnect the center channel.  The factory amp has all the crossovers, so the tweeter will fry if you try to hook them up without adding a cap.  Also-the factory speakers are all 4 ohm, so if you parallel the tweeters with the door speakers, it will fry your head unit (2 ohms).  Some people series them (then the tweeters will play full range- ugghhh), but then you have to fade toward the front to match the volume level of the rears (8 ohms).  Of course there's always the option of leaving the tweeters disconnected and just running the door speakers (4 ohms).

If you're running wire to the speakers, you might as well install new component speakers up front.  This will give your new deck a 4 ohm load on all channels without having to lose your tweeters.