Any feedback on Rythmik Audio Subwoofers?

I am looking for a new subwoofer to complement my Green Mountain Europa Speakers. Specifically want a music sub, not HT. Roy at GMA likes the Dayton 12 MkIII for a low price solution (since I can't afford his!).

Does anyone have experience with the Rythmik Audio sub's? How about with Direct Servo solutions?

Thanks in advance!

Drew