I have the good fortune of owning two System Ones. One standard system and one rare "high-power" configuration using 2 620 amps and the uber-rare BA-100 bridging adaptor. These 2 systems are both near mint and truly the cornerstones of my vintage collection.
The standard system does have two preamps....the lower unit with the analog meters is a mixing preamp. Very versatile, you can hook up a multidude of items to these without breaking a sweat!