I had a 2100.1d a couple years ago. I liked the sound, the footprint, the power and the efficiency. I currently have a bb2400.1 and it doesn't seem to sound as good as the mmats i had before.
One sold on ebay for $311 shipped on October 19th 2014.
Mmats M3000 1D Amplifier | eBay
I dont know if its the same model you have or if you have the newer one.
I signed up for this website hoping to find an Mmats HD4000.1 amp. If you have one for sale or maybe trade could you pm me please? I check here, CACO, and ebay regularly for one. Thank you.