I've never used any Panasonic headunits before so I don't have any input as to whether they are good or not, but that model does seem to have plenty of rca outputs for what you need. As far as speakers, that's pretty subjective, and installation will play a bigger role. I would try to use some speaker adapter made for your car, and fit a circular driver, 6", 6 1/4", 6.5". If you had planned on getting a bl, and running a lot of power then you likely would have needed batteries and or a high output alternator. The way I see it is you don't want to spend a billion a dollars, but you still want something better then your average car, and much louder. You can use a large enclosure for the subwoofer, you'll gain efficiency, use a smaller amp with no ill effects, and gain some more headroom for the power demands of another amp for the front speakers.