i mean, sure for 450, you could have had a "more worthy" sub stage. P2s can be had for 40 bucks new, a box that im assuming you got from best buy? would be around 30-35 bucks, and the wiring kit (assuming its decent) would be around 50 or 60, then the install would be free if you did it... so yeah you could have used the money for more powerful equipment but it seems that youre satisfied with it for the time being so dont fret. i would advise you to look around the forums more before building your next system and youll be far more happy when youre done. not hatin or anything. twisted is right in his thinking, although harsh, but if youre happy then good stuff.
the scratch is purely cosmetic and doesnt matter at all to the performance of the sub itself. if you feel that it ever does, just throw some CA glue in the crack and it will solve any problem that could arise. stick around the forums though, youll learn a lot.