I haven't tried this with a keyboard...but works great as a home sound system and guitar amp.

http://www.sweetwater.com/store/detail/Amplifi75

In addition I use it as a Bluetooth speaker for my iPad

reminds me of the Mackie Freeplay

http://mackie.com/products/freeplay

Recently I test-drove the Freeplay at a local GC. I had my insrument. So I was playing pretty much a full range of frequencies. I sat just a few feet in front of it and I was not impressed with its performance especially the lows.

no surprise there with these small speakers lets face it for low end you gotta PUSH AIR!!

Probably no comparison to the big Marshall, the Aiwa Exxos and the Bose Sounddock 10, whose bass really makes the room shake.

A great thread. Thanks for the link. How do you compare your Sounddock 10 with the KMC-3? I've been shopping for either the Exos 9 or the KMC-3. Now that you mentioned the KMC-3, I would have to bid against other members on eBay! LOL I like the small footprint of the KMC-3, but 8 D batteries would be a deal breaker and kind of defeat the purpose of its own portability.

I agree, but some of these small speakers mentioned by Rosetree seem to have a better performance/speaker size ratio. I really wanted to like the Freeplay for its pro features. Besides, by the time you add the optional battery it gets expensive.

I wonder how the Roland KC110 would compare with some of these new big sounding speakers. The KC110 is only 20 watts running on batteries. Then again, the bigger BA330 is also 20 Watts or so on batteries,but full sounds. Taking out the battieres in these units is a real chore, and I had a friend install a charging jack as shown in the attached pic(if I uploaded it right).

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 ...

Rosetree, very useful info. Thank you