box design, check it out

ok, so ive been using winISD pro alpha to design a box for my 10" punch HE sub. so far i have it worked out to what i know i would want my home audio sub to perform like, but was wondering if it even mattered in a car. the reason im not just going ahead and building it is because i wanted to make the box where i would still have cargo room, but in the trunk of a 91 civic there isnt much room for a 2.3 cu. ft box to blend in.
the curve is very flat down to about 22hz, just about +/- 2 db from 80hz to 22hz.
i was wondering if i would be able to tell a difference, as reducing the box volume makes the curve drop off toward the lower frequencies, ruining the linearity i was looking for. it is, however, alot more linear still than the sealed box i have now.

Best thing to do is measure the cargo area and see if you can build an odd-shaped enclosur for the sub that will maximize use of trunk space.  The larger size would still be the most ideal for a car, because the gain you get from the cabin wouldn't be in the very low frequency range anyway.  You are maximizing the lowest bass (which you'll get very little of in your music, btw...) by keeping the box large.  I may be off a little on this, but I'll bet you don't get much below 40 Hz in music.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

i just want to be able to have that extension. i listen to alot of electronic music (DnB type stuff) and also alot of classical and organ composures that will get down pretty deep too. you think id be able to tell a 5db drop between 45 hz and 20 hz?