ok, now i understand, you left a hole for the bass! cool, but don't you miss those speakers?
yes, i cut out (2) 10" round holes and basically used the rear deck, along with some wood, as part of my box, firing straight up, and reverberating off the rear glass. best sound yet.
...already tried the armrest idea, as i had a different custom angled box pointing toward the rear seats and lowered the armrest when i wanted extra bass. i thought it was a great setup, as a slide-out tray was fabricated over the speakerbox to hold the 2 amps and a 10 disk cd-changer (which is still worthless with subs unless at low volume, everywhere i put it, the bass knocks the cd's out) wiring caps and distrubution blocks. the only drawback to this setup was that the spare tire could only be removed after the speakerbox was pulled out...unfortunately, i blew a set of 10" speakers like this because one shorted out and took the other one with it as it was handling the full 1000 watts from the amp by itself. then the amp fried shortly after that. luckily, the 10's were under warranty so i re-soldered it back onto the cone and it sounded great for about a week when the same thing happened when i got a new (1200 watt) amp!! then i had to wait 5 weeks for new 10"s to come from the dealer...
after all this frustration with the speaker dealers, it was decided that the best possible setup was to cut the decklid and to hang a box from it was the only option for maximum sound with spare tire access, with amps mounted on the rear. it was installed 8 months ago and i've had no trouble since, plus 3 times the bass. that trunk it just too tight to throw a standard box in!!
there are some pretty sweet rides on this site below (in my signature, look near the top of my page for the "BMW 3 series" links) to get some more ideas from, but beware! as there is some major ricing going on...i didn't think you could fit 19" rims with hydraulics on an E36...