The way it works;

Signal comes from source, tuner/cd/tape, etc. and goes to a pre-amp. Pre-amp boosts the signal a little and sends it to the power amp. The power amp drives the speakers.

Some head units are only a source and pre-amp, to be used with external power amp(s), some have an internal power amp.

That head unit sounds like it will work with or without the factory power amp. Sounds like it has its own power amp that can be turned off so you can use the factory amp instead.

What make/model are you looking at?

 

Kenwood Excelon KDC-X689
http://www.crutchfield.com/S-3d9Zdkd...113KDCX689#Tab
(it says the item is no longer available. that's because I bought the last one)

I pulled apart my dash to find the amp. Could they have tucked it away in a tighter spot and then used longer bolts to mount it? It's got the plastic plugs like someone else had already stated. One fo the guys in the techincal forum said that I don't have to bypass the amp. That's all he said. He didn't give me any more details. I did some searching around the internet and found that Metra makes a couple of amp bypass harnesses (1 for the handsfree setup and 1 for the setup without handsfree). I'd like to get a difinitive answer about bypassing the amp. Another guy had the same question with his 2003 and he was told that so long as he connects the blue wire on the new harness to the remote turn on wire on the new head unit, the amp will work.
Link to dodge forum: https://dodgeforum.com/m_720677/tm.htm

 

What I gather after reading the literature is they have pre-amp outputs for use in you own power amp.

I didn't see anything about shutting off the internal power amp, but with those preamp outputs, you can run the unit to the existing amp with a little wiring or maybe somebody makes a converter.

The stock power amp is designed for you stock speakers, so that is probably the way to go.