Sorry everyone.. The forums aren't emailing me so I have missed quite a few posts..
GezusK: I recharged my mouse when I first got it as per the instructions. It hasnt needed charging again (about 1 month ago).. You could probably wire it to use the car power supply but... it's totally unnecessary. It wouldn't stay hooked into the base very well anyway while you were driving. You could always buy a second battery and the standalone battery charger.. Go to Gyration's web site to see what I'm talking about.. But really, the charger in the car is not necessary.
Cool. E36 M3 definately has its place in the M3's. Do you get Roundel? They had a nice article last month about the three generations of M3's and how each is better suited to some things. My last car was a E36 328iS (Sport Packages) .. so driving my "Almost-an-//M" made me plenty jealous of you E36M3 guys for plenty of years
Anyway, my electrical setup is correct I am using an OPUS for power so it's not a ground loop thing. E46 also uses balanced audio to feed the factory amp, and I'm using a Peripheral VEN4 to interface with that properly. The audio problems are due to the crappy onboard audio as I can hear faint HDD noise, etc. Another reason to go to USB audio from the onboard EPIA is that I won't have to listen to the PC speaker "Beep" during POST come through my car speakers. It's rather annoying... I'll probably go to a M-Audio Sonica at some point though it's not really high priority.
Yes I used an IDE<->Firewire bridge board. I just used one I got out of some cheap 3.5" enclosure from CompGeeks.com.. It was about 20 bucks and supported Firewire and USB2.0 with the Oxford911 chipset. I had problems getting my CD-ROM to work on the firewire interface and had to reflash the OXFW911's firmware which was a real chore, but worked OK in the end. This shouldnt be necessary unless you have a problem with your setup. I had it working with other CDROM's without a problem.
Just buy a cheap external 3.5" HDD firewire enclosure somwhere and get the bridge board out of it.. it's pretty easy to do really. You can order bridge boards seperately from some places, but I've found they are usually far more expensive than just ordering a firewire chassis on sale...