Wow, you're set up nice. Last time we had a power failure here, just for grins, I tried to get on the internet with all my equipment plugged in to a UPS. Computer, router, and cable modem. No dice. I assumed my ISP was down as well because of the outage.

UPS's are great. Like you, I have four of them (even including the dead one with a defunct battery!) During outages my SOP is to use the UPS's to shut down all my computers gracefully, then move one over to my digital piano. I found that a single 550VA UPS will power the piano for four hours (using headphones, not the built-in amp and speakers). Not bad. There's something fun about playing piano in the dark by candlelight. I've since bought an acoustic piano too, so I don't depend on the UPS's so much for piano playing anymore. And luckily power failures are usually short-lived and fairly rare around here.