Good to see that there are other solutions out there.
Unfortunately, the one you propose is way out of line from a cost standpoint: even at the discounted price, adding an appropriate amp and driver would effectively triple the cost of the system...not to mention taking up valuable (to me) luggage space. Upon review of their website, I can't tell if the "group buy" price includes an amp and driver or not. Either way, too much $$$ for po' old me.
Also, I would like any responders to please note that, in the OP, I stated that I had been happy with the Kenwood SW1 series under-seat unit...I would have happily recycled it if it would have fit in my new car. I am a 64-year-old jazz, country and soft-rock fan. If you can hear it outside of my car, it will probably hurt my ears.