I've tried to get all my components I've owned (Infinity Kappa Perfect 6.5", OZ Matrix 180cs and lots of CDTs) to play lower than 200hz, and it just depends on the door. I've gotten much better response out of my VW GTi than any other car I've installed on... and bass response out my my Nissans without special (sealed) kickpanels seems non-existant in comparison.
So my solution (when I used to run a Cerwin Vega IT 15 in my SQ system) was to run two CDT EF-8's. I put them in .5ft^3 boxes under the dash, and crossed my 6.5's somewhere around 220hz IIRC. You can get away with 5.25" mids if you cross em that high. The ef8's are cheap too, I think I ended up getting a pair brand new for $100 or so.
So get some decent components (I recommend CDT's with the CL62 mid, SatNet560, and the TW26 tweets - should be around $250) if you can give em more than 50w clean rms, and some very responsive 8's to fill in.
Crossovers become important (people with 4way setups almost always run active), but can be done passively... I didnt worry about subsonics/etc on the 8's because they were in sealed box, but i did run something for the top (don't remember exactly what i used).
I know that's a little more than your $200 number, but to be honest, you won't be happy with a 15" and 6.5" components. Too big a gap.