I just got home from GC - I bought a second CM-30. I plan to use them with the G70 as a mini PA and at other times as monitors. They are built like tanks and sound solid too. Even the young salesman who hooked it up to check for defects was impressed by the amount and quality of sound. These cubes are way better than any of the new Street Cubes that Roland is pushing; those are mostly underpowered mini-guitar amps. The CM-30 is a solid unit; one would be sufficient for a small audience of say 30-40, but a pair should be able to handle up to 100 people easily.
The sound is solid, with decent bass and good high end; a small sub-cabinet would make this unit rock unbelievably. I haven't had any need to run this box at top end, it's that strong. I have the channel and master volume set at about 1 o'clock; the bass at 1 also and treble at about 11 o'clock - it sounds great to me. I have mine attached to mic stand adapters; they snap on and off. When not on the stands, the adapters help tilt the cubes like monitors - very cool
As for the Mackie SRM 150 or even the Alesis 50, both are more expensive and have the same features. The Mackie boasts phantom power and 150 watts, but I wonder how that was calculated, as it has only one 5.25" coax speaker - way too many watts for that kind of speaker.
I was lucky to get mine as used returns; I paid under $200 for the pair - at that price I couldn't pass them up. Now I'm glad I didn't.
[This message has been edited by cassp (edited 10-13-2007).]