Well, a lot has changed since then. When dealing with the people at Mac Car you have to be very specific on what you want them to do. Budget and how much you're willing to pay for an install is also another factor. Sure there are many places that can do amazing work, but how much do you think they payed for it to be done? When I first got into car audio I spent at least 1500.00 for installation + a custom trunk install. Which with lots of patience I could of done myself. If you're willing to take the time you can sucessfully duplicate any custom install. It just takes time and money until you get it right. BTW, there are many books available that teach and explain the basics to car audio installations so really anyone can do an install. The question is are YOU willing to take the time to do it?
I believe they've done two E46 M3s, actually the owners are members of this board. Maybe the best thing for you to do is ask them their options of the work done by Mac Car, it can't hurt to try.