Pal,
I bought the S100 ( not S-100 ) and the Linestage brand new when they first came out in 1991. Both of them feature dual mono configuration. The S100 employs balanced inputs exclusively, therefore should you choose to use the S100 with an unbalanced signal, adaptors are needed to connect the single-ended cable to the balanced input. Of course, this is not recommended for long term use so you must be prepared to mate it with a pre-amp with balanced output. The Linestage is probably best matched with the S100 but it is rarely listed in Audiogon. The S100 is designed to effortlessly deliver the high current required to drive low impedances. I was using it to drive my Thiel 3.6 which is known for its difficult loads of 2-4 Ohms. The stiff power supply uses custom made capacitors with 160,000 microFrads of reservoir capacitance. With 24 Sanken 20 Ampere output transistors, the S100 is specified at a nominal 2 x 100 Watts in an 8 Ohm load and can deliver peak power of 2,000 Watts in a 1 Ohm impedance.
While the S100 to outward appearances resembles a stereo amp, it is in fact more accurately described as a two-channel mono amplifier, with only the AC input and the On-Off swtich in common. Beyond that point, the topology of the S100 is strictly dual mono, beginning with separate power transformers and including a metal partition separating the two mono amps to eliminate any possibility of interaction between the two channels which might potentially compromise ultimate sonic performance.
If you need any further technical specifications or further information on the S100 and the Linestage, pls feel free to e-mail me.