Asus MB, PII 266, 192 MB Ram, 6.8" LCD, 6 Disk CD-ROM, 21 Gig HD, All-in-Wonder Video w/ TV Tuner, Irman, Windows ME, Winamp, Cobra III -- All in a custom acrylic case.
Accually, Plexi glass is a very horrible material to make a sub out of.
1. It resonates very easily causing a really nasty sound curve.
2. It is a reflective material. The back wave that is made by the speaker should be absorbed (sealed enclosure) or directed (bandpass enclosure). Plexi will have a tendency to reflect the sound to create harmonics which will cause your sub to lose definition and yes, power.
Just as an example, a very porous cement is the best speaker enclosure. srtong so it will not resonate, and porous so it will not reflect. Keep these things in mind when bulding your speaker box.
UPDATE: I moved farther north. Now its even too cold for the deer; only moose now