Ditto to what Scott said - I use my KP-100s extensively now, and I have not changed out the speakers: my amp is completely stock. I play a couple of small restaraunts that are very picky about sound volume and the KP-100s has impressed them so much (and me) that I decided not to switch out the bass speakers. Also, the KP-100s is comfortable to carry and I didn't want to add to the weight, and it fits in my car trunk perfectly. It's a great-looking stage accessory too.

I don't know anything about the Logitech speaker system other than what has been posted here, but again I would side with Scott on the KP-100s being a more professional unit with cartage and stage use in mind.