Ed, I think it was a USB hub failure that locked up my computer as the problem continued on UPS until I moved the USB power supply onto the UPS power. Whether or not six Behringers with switching supplies will suck enough power at turn on to create much of a surge has a lot to do with power routing and the dynamics of the event which can vary just based on power line distances and how much of the surge gets absorbed in the wiring without tugging on the computer or external USB power. It's all on one 15A circuit which is plenty under the static load when all the power supplies are stabilized.
Another solution would be to sequence the power so that not all of the monitors powered on together. The choice of Uninterruptible Power was driven in part by my desire to protect the server grade hard drives and a Samsung EVO SSD from power issues. UPS is just a good thing in general and I was surprised that the largest unit stocked at the local Best Buy was on sale and very affordable.
The other USB hub issue I had was that with the computer on and the USB hub power off this particular model tried to power my encoders from the computer USB port where the USB hub connected. The computer USB port failed, presumably from trying to supply more than the normal 600mA. That is NOT how I would design a hub.