Im looking to replace the headunit but I dont know much about the audio system in it. If anyone can help, I have a few questions.

1. Do I need to rewire the speakers?
2. What ohm load are the speakers?
3. Where are all the speakers?
4. What happens to the little audio button in the center console?
5. If 2 midgets with severe ADHD leave in opposite directions running from the same spot, how long will it take for them to run into each other?

I have never worked on a touring, but I am assuming it is smilar to other E46's:

1 & 2 - each speaker has it's own channel of amplification, so it wouldn't be practical to keep them and have to build a custom passive crossover for each speaker. A lot easier to bypass the oem amplifier + get new speakers, or keep the stock amp+speakers with the new heaad unit, which will not give you any improvement in sound quality.

3 - front doors, don't know about rear

4 - will still work if you keep the stock HK amp, otherwise you get a free switch for other purposes (with a little rewiring). I used mine to turn my V1 + laser jammer on/off.

5 - when the trains run into each other in delaware at 3:05 PM.

to reuse the factory amp I would connect rcas lines to the factory amp leaads coming from the radio harness in the dash and run them off of the rca outs on the new headunit I assume?

No, just use a wiring harness with speaker levels out of the head unit. You also need an antenna adaptor and trim kit, of course.

thats a new one. The infinity system uses a high level input for the factory amp? Thats frikkin sweet. thanks for your help.

thats a new one. The infinity system uses a high level input for the factory amp? Thats frikkin sweet. thanks for your help.

Not exactly a high-level input, but works.