OK, so using the Seasonic PSU calculator, we're looking at least 670W for that machine when running full tilt for games approximately. No including Monitors/Displays or the router.
The issue we're up against however, is PSU up time. As far as I know, for consumer UPS, there's no UPS that can deliver that amount of power for more than "minutes". So anything up to an hour. Not at an acceptable price range anyway.
I think what you'll need is something like those generators or inverters (for that much power and that much duration, which is outside what most consumer UPS would handle), both of which is outside my knowledge and wheelhouse, so someone else will need to step in regarding options for those (but I know we have several members on the forum who are experienced with that stuff, so you should be covered).
You "might" be looking at using a combination of the two UPS + Generator to be able to keep that system up. But again, outside my domain of experience so just theory at the moment. But if I'm right, it's UPS to keep the system alive, then when the generator detects the line has gone out, kicks in and keeps the UPS up. But there's some frowning on connecting powered stuff like that in serial, so wait for the experts to chip in on that first.
Most of the UPS that can handle that load (temporarily) are in the £250-£380 range. The generators/inverters are more, but you can take all of them away with you to wherever next if need be too.
Sorry I'm not more help here.
