Back with a new ride!

Hey guys, I'm back. After all the great advice on the old integra, I built a great-sounding low-budget system with a Honda premium HU, pyramid 6.5" woofers and inductors in back, and infinity 6.5" up front. Loved it, but traded the teg for an '05 Mustang.

So, where to begin? I got the "Shaker 500" audio option, supposedly 8 speakers and 500W total peak power. I plan to keep the head unit for now since it's got a 6-disc changer and mp3 (and obviously I have an affinity for factory heads). I'm not even sure of the layout but assuming an external amp, there's also a pair of what seem to be 8" subs in the doors, some kind of speakers above them (crutchfield says 6X8 fits) and I think 6x8 in the back. The head also has optimizations for all seats, front seats, and rear seats -- seems like some kind of time correction?

So, advice? The sound is powerful but lacking in mids, clarity, warmth, etc. I'm hoping I can find the amp and upgrade it, replace at least the front speakers...