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.
Do you have any thoughts on buying a 610 or a 630 unit as a preamp for a non-Nakamichi system? I think they look cool. It is an idle thought I've had for awhile.