So I bit the bullet and bought a double din touch screen unit to replace my factory CD/Cassette ... I'm old, I like using CD's. I really had no problem with the factory set up other than the new unit was shiny and I have a problem with NOT buying things for this car ... even if they're not necessary or even really wanted.

Ok so basically, I've installed a lot of aftermarket stereos in my day but, I've never installed one in a car with a factory amp (all the OEM ones I've replace had the pre-amp built into the unit). I was wondering if I had to do anything different when installing this unit than I would say an other/older import? And do I have to do anything to the unit as the unit has a pre-amp built in and then I'll have the factory one too. I just don't want to either **** up my factory amp or the new unit by frying something. Thanks!

I've had a few head units in a couple of different Celicas with the 6 speaker setup. There was one plug I pulled from the factory amp and the other plug was from the factory head unit. Otherwise, the dash harness adapters do the job perfectly. I believe the head unit draws power from the amp.

This is what you need if you don't want to bypass the oem amplifier.

Metra 70-8112 Integration Harness

otherwise, you can wire the speakers individually using the typical Toyota stereo harness (from Walmart or where ever) and use the built-in amp from the new stereo.

You need to unplug the white plug on the back of the amp, because you need to wire your stereo into this harness. The blue plugs are useless

If I bypass the factory amp, and just hook everything up using your basic aftermarket radio harness, will I still have my door tweeters? I've never done this on a vehicle that came with more than 4 speakers. I've ADDED component speakers, but I needed a separate amp for them.

The blue plugs may be useless, but definitely leave them plugged in or find a way to bypass them. Unplug them from the amp and your head unit won't have power.