old post I know,,,,,,,,,i picked up a C1/M2 (non A version) for $40.00! I hooked it up with and without the sigma drive. I was surprised to hear the difference. I was not too impressed on the sound without the Sigma Drive hooked up and thought all these years of curiosity were for nothing, then I hooked up the Sigma Drive and was pleasantly surprised. It sounds Great! Plenty of power and very nice sound!
I picked up an M2 a couple of years ago for $50. I think it is a great amp, very punchy on the low end with over 1000 damping factor. I have never hook up the sigma drive though. I guess I will have to try it and see if I can tell the difference. I have it running a pair of JBL 4412A studio monitors.
Wishing I could post in the Ultra Hi-End HT Gear ($20,000+)
I have a basis M2 in use now..not useing the sigma drive either...but it does have some good power @220 watts RMS @ 8 ohm...and around 325 RMS @ 4 ohm ( which it currently running at) has an internal fan which it has never got hot enough to come on yet...great amp for the $$