I've read a few posts sort of doing what I'm trying to do but it's not very clear. I have my old 2000 D2 with the Harman Kardon system in it. I bought a 2001 D2 that has the standard system.

Is it plug and play transferring the system from one to the other? I'm replacing the head unit with an aftermarket one (though they're both the same regardless). Obviously I'll have to transfer the speakers too though those should be easy as long as I don't have to mess with wire routing as well.

 

Buy a wiring harness for your vehicle off of Ebay and wire it to the back of the new radio and then unplug your old radio. Plug in the new radio and that is it. I put a Pioneer flip out 7" screen and there is very little room behind the radio so utilize any and all space you can. Just take your time and it will be an easy 30 minute to an hour job. The increase in watts will make the speakers sound much better than the factory radio.

 

Yeah I have the harness already for the high line system from my other D2 (bought from crutchfield with the head unit).

I was more asking if I could swap the whole system over as I wanted the harman kardon components. I'm thinking I still have the harman kardon speakers and whatnot because I DO have a cd changer and the 3 front speakers...the only difference is my 2001 doesn't have a speaker grille with the harman kardon badge on it.

 

If you are doing this just for a sticker, I do not understand.
I worked at a Harman Kardon professional audio factory in US and know that all modern automotive systems are tailored to fit the acoustics of a specific vehicle the equipment is made for. (A production sample vehicle is audio-analized and tested when the audio equipment is designed) It is not like the seventies when there was no matching engineering.
A transplant to another year should not vary much in relation to the room size and characteristics, but keep in mind speakers and amplifiers are matched for the best. Do not mix components brands when possible.
Using aftermarket equipment may not equalize properly for top notch frequency response.

 

I'd suggest just buying a decent set of new speakers. Depending on if you're adding an amp or not, you can still get some good sound without spending a lot.