clonestar,
yeah, i imagine more sound would come out with the speaker grills, but as it is, i left the back side completely open to help the sound flow out. i usually keep it at around 75% volume, anything more and you can't hear yourself think

you are correct in regards to how i wired it, that being a splitter on a single stereo jack, and i was concerned about how the quality would diminish, but surprisingly it didn't even come into play. the subs are amped (by stock design) so i guess that makes a difference. . . but then again, i am happy with my stock stereo in my toyota truck so i am by no means an audiophile
