We are the North American importers for BMC, and this is just an information post on the BMC Products.
Regarding the AMP S1 stereo and AMP M1 mono: These amplifiers can be run RCA, XLR or XLR CI (CI stands for current injection). A short description of CI (Current Injection): Low-impedance signal input that lets the original current of the signal source flow through the amplifier circuit until it reaches the desired speaker output voltage. When running the CI analog outputs from the BMC DAC1 to the S1 or M1 amplifiers CI input you activate the current injection feature. In addition when you run a Toslink cable (included with amps) from the BMC DAC to the amp this activates the DIGM (Discrete Intelligent Gain Management) feature. Then the volume is done inside the amplifier eliminating the need for a preamp. The DAC1 PRE adds additional inputs for other sources and can also be routed through the Current Injection circuit. The DAC1 also includes HR-USB 24/192.
For a introduction to the BMC Amplifiers have a look at this PDF:
AMPLIFICATION REDEFINED CI DIGM LEF,
http://www.bmc-audio.de/en/pdf/BMC_Amp_amplification_redefined.pdf
The BMC products offer many new advancements not seen in other high end audio lines, including modular designs for future upgrades, large production runs of 300+ units per product and a unique marketing plan offering the consumer a fair un-inflated price.