the current setup in my grand prix is JL xr components all the way around on a 300/4 and a single 12w3v3 in a HO box from JL on a 500/1. i enjoy the way it sounds. its pretty dynamic and plenty loud for my taste. i ran the 500/1 on a pair of 10's for several years with the mids just off the Alpine 9813 deck (back when alpine made good decks) it always sounded fine at moderate volume but was seriously lacking if you wanted to turn it up.
in my truck i currently run JL c5 components all the way around on a 600.4HD amp and a pair of 10's under the back seat on a 750.1HD amp. in that case the mids will easily overrun the subs due to the physical driver limitations of the 10's and the space they are confined to. short of giving up the back seat or a custom enclosure for larger subwoofers its about as good as it gets IMHO.
i prefer the setup in the grand prix as it is more balanced.
some where around 50-75 watts per channel on the mids and 500 watts per subwoofer driver should be adequate for most people.