While a/d/s/ are some of my favorite drivers out there, they are FAR from budget.

I would try the crystal comps on sounddomain, or for low powered applications, Infinity Reference. If you have a bit more juice, try the Kappas.

I really think that you should just do the fronts, and try to get a small amp on them...that would be much more beneficial then trying to power all 4 sets from a headunit. The more power you feed them, the louder they will go without distorting...hence they will be able to keep up with your bass.