Pay no attention to power ratings. You can not under power a speaker.
When I say driver, that's just a different term for speaker, subwoofer, etc. . . So a quality driver would be a subwoofer of quality design and build that fits your application. The old adage of "you get what you pay for," certainly applies here, but it is pretty simple to spend as little as $100 and still get a quality sub.
If you want to use SSA, subs, I highly recommend them. I have no experience with the new drivers, but do with the older stuff, and they make a quality product with excellent service.
As for the processing, you can try the LOC. I don't know how the factory handles processing. Some are done in the headunit, but most have a separate processor/amplifier combo. I would do a bit more research to see if could tap into the signal before it is processed such as getting it straight off the head before it hits the factory processor or amplifier.