First thing I would do is ditch the bandpass. They do nothing but muddy the sound in an attempt to compensate for an underpowered system. In a decently designed system with a box made to the right specs for the sub, you don't need the bandpass at all, because it will sound great as is. Also, I personally wouldn't run a Kenwood amp, or RF anything, but those are just personal preferences. I do like Pioneer head units, as I've had probably 6-7 of them. I don't know what you're aiming for, but personally I prefer having good sound rather than overbearing bass, so I'd probably spend a bit more on the front and rear components, and have a little bit weaker subwoofer, but at one time I did the big bass thing too, when I was younger. Now, I'd probably be happy with some Infinity or MB Quart front and rear speakers, with a single 10" in the trunk. But that's just me, and trunk space in a mustang is at a premium anyways, I don't want a huge box taking up all of my trunk.