While I agree that cutting into your Tour Pak would be tough to do, I've seen, heard, and asked about this kit when I was in Sturgis. The kit essentially turns your Tour Pak into a sealed speaker enclosure by adding what they call "sound sealing technology" foam parts that prevents water leaks and helps seal the Tour Pak. The guy I talked to said that going from the relatively small unsealed volume of the rear speaker pods to the at least tripled sealed volume of the rear speaker pods and Tour Pak gives you a huge jump in bass. More pressure and volume translates to more low frequency response or bass. It really doesn't matter what kind of speaker you throw in the rear speaker pod because of the limited volume but that is fixed with adding this kit. I've been told that the bass can still be heard very nicely on the road as well.
The kit appears to be pretty easy to install as well because they include a template that locates on the three speaker pod fasteners that you use to drill a pilot hole for the 2" hole saw.
I've been looking upgrade to a '10 or '11 TK and when I do this will be the first accessory I buy for it. I'll actually be getting the Ultra Boom Bagger kit that comes with the port kit and amp. Can't wait!