The instructions I posted on Sounddomain should answer your questions. I used the original BOSE speaker pods. My Focal mid-bass drivers fit perfectly. I originally put the cover trim ring back on then removed it after listening. I did this because it sounded like the speaker cone was hitting the front trim. As far as the rear clearance, there is maybe a couple of millimeters but it is vented and sounds great. Really tight mid-bass with no distortion at very high levels.

http://www.sounddomain.com/member_pages/view_page.pl?page_id=133487&page=4

As far as your ideas on line-drivers, eqs etc? what are you going to use for a head unit.

I originally intended to use my factory head unit. When I added amps and speakers the sound definitely improved. I soon chose to change my head unit to a high end Nakamichi with 4V line level outputs. The sound improved VERY dramatically! I cannot accurately describe how high the sound quality is. It is dead silent (no-hiss) and very dynamic. I cannot recommend a new head unit, quality amps, and speakers MORE strongly.