Yes, there was…
The problem is that the M1000’s will transmit 44.1kHz data at 44.1kHz, while the M1001’s will upsample the 44.1kHz data to 48kHz…
The upconversion in the M1001’s will mangle the DTS encoding, and your receiver will not be able to decode it… Theoretically, the M1001’s should be able to play DTS content encoded at 48kHz, but I don’t know if it works.. (I only have an M1000 and 44.1kHz content, off those DTS CDs)