Threshold S300 Power Amplifier

This is my first foray into the high end area of audio. I have a few questions please. By the way this amplifier will be used with Magnapan 1.6 speakers eventually. Right now I am using Mirage OM-9 omni speakers. They are 6 ohms. These sound to me like the original "Time Windows" for anyone who remembers them. The amp has already been serviced with new caps, speakers terminals,etc.

1. Does anyone know why Nelson Pass decided to make class A and class A/AB power amps? I've heard that class A amps are sweeter and more warm than class A/AB. Is this a fact?
2. What pre-amp that can accomodate at least 2 reel to reel tape decks and the Original Elite Rock Turntable sound great with this amp?
3. What power cable, speaker cable and interconnects will make this amplifier sound its best? I listen mostly to large and small scale choral and orchestral works as well as jazz groups. I love a warm sound and the sound of the human voice especially choral works. I am willing to listen to and learn from all comments. And I plan to benefit from all that's said here. Thanks so much.