While the Kappas would sound thin in smaller boxes when placed in a typical listening room, remember that in a car there is such a thing as "cabin gain". That means that within the confined space of most vehicles, one can reasonably expect a rise of approximately 12 db/octave in overall bass response from 60 Hz downward. Having subs that are -3dB at 50Hz is actually a pretty good design for most vehicles, and I think that if you follow manufacturer recommendations for most car subs that is the alignment many of them suggest. Because I don't know what kind of vehicle these are going in, I can't say for sure just what kind of response you'll get. But if its anything smaller than a Chevy Suburban, I'd say you'll get pretty amazing bass in your smaller 2.7 cubic foot enclosure.

Believe me... considering that most decent car audio subwoofer drivers are only about 88dB efficient, the Kappas when given moderate power should be just about able to make your windsheild wipers bounce off the windsheild!

Have fun!
Colin