I suspect a standard 20A 110V circuit can probably handle 2x RTX 6000 Pros. 15A probably can but that requires more research.

During initial setup of the server I am putting together, I found that a machine with 4x Blackwell cards derated to 300W can get by on a single 120V 20A circuit. It's tight but doable. A lot depends on the power supply. I don't think it's a great idea to run 4 high-power GPUs on a single ATX-style PSU, even a beefy 1600W job.

The other questionable part is whether all four cards can temporarily spike at full power during boot, before the wattage limit is applied by the OS. Some accounts say this is possible, and if so it could shut down the party in a hurry. But I didn't see any misbehavior when I tried it.