I'd look for an Infinity Basslink. I absolutely love mine. 10" sub / 200W Class D amp. Variable Phase and Adjustable Crossover & Gain.

Not boomy, but hard hitting, crisp bass with excellent clarity and control for such a compact, easy to install product.

BTW, it only takes up about 3/4 of a cubic foot. Very compact. Mounts fairly easily to the folding seatback. Use expansion anchors and Dynamat under the carpeting though.

They're about $350 at Crutchfield; they've been on the market long enough to come up on eBay, IMO.

My 2˘