2006 lexus is25, aftermarket amp

Ok so Im trying to install a double din into my 2006 lexus is250. The problem is that in order for me to install my aftermarket HU I will need to bypass the stock amp. So I want to run all the speakers through my aftermarket amp and run it through my double din. The problem is that the is250 has 13speakers. How would I go about wiring it to my 4channel amp?? i have no idea how to do this.

take a look at the Metra TYTO-01. Its an amp integration harness to keep the factory amp functional with an aftermarket headunit. If you want to use the 4 channel amp it shouldnt be a problem. I'm not sure of the exact setup off the top of my head but more than likely the car has a variety of different speakers - midrange drivers, tweets, center channel, etc. In most cases, impedance wise, tweeters are irrelevant because of them being designed for high range freq. the only problem you may find is the center channel

Oh ok, so you think it would be better and easier to use the Metra harness then a 4channel amp? I looked up info and it look pretty easy to install.

If you are simply using the stock speakers than I would toss the 4 channel away and use the module and call it a day, you'll loose less hair in the long run ;)double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

I do like my hair. haha ok ill order one!