Originally Posted by nick325xit 5spd

The short answer is that BMW's modern 3-way system is quite nice.

Why? Because you can install a robust midbass woofer and take a lot of stress off of the midrange driver. A 4-5" driver is generally going to do a lot better for the vocal ranges and is more able to meet the tweeter at the crossover frequencies that it will want. It also lets you take some of the upper range off of the subwoofer.

My crossover points in my E90 M3 are roughly 4500-200-60. With a 2-way setup, you generally end up at crossing the mid to tweeter at 3500, and the subwoofer comes up to 80 (or higher if your mid just can't get there).

That said, getting a driver under the seat requires space that may not really exist in the E53.