I tested them side by side yesterday in my apartment. Consider that the KMC-3 only weighs 3.5 kg, the Sounddock 10 weighs 8.4 kg, almost as heavy as a HK Nano 300. Given that difference in weight and the smaller shape, the amount of deep bass coming out of the KMC-3 is surprising. Overall, it can get really loud for a middle-sized living room, but the Sounddock 10 gets unbearably loud at maximum when standing in the same middle-sized room. I'd say subjectively twice as loud.
I also once compared the Sounddock 10 with a Bang &Olufsen Beoplay A8, which is rated 210 Watts RMS in total. The Sounddock 10 was considerably louder than the Beoplay and had a little more vibrating bass, while the Beoplay had a more precise sound with more stereo.
If you took the 230 Watts of the HK Nano 300 as representative of how "loud" it is in terms of human perception, the effective wattage I would give these different systems would be

HK Nano 300: 230 W
Bose Sounddock 10: 180 W
Beoplay A8: 140 W
Klipsch KMC-3: 90 W
Beolit 12 and Bose Sounddock portable: 60 W
Bose Soundlink III: 30 W

This is a subjective ranking based on tests I've done comparing two or more of these systems directly in our home over time.

Even if the Sounddock 10 has massive bass for a one-piece home system, it has audibly less bass than the Nano 300 (no wonder, it's a 6.5 inch subwoofer against a 8 inch), but stronger highs. Its weak point is the limited stereo width.

Here's a pic of a test from last year (I don't own all of these ...