When dealing with multiple devices, it is always best to power cycle them in sequence (one at a time), rather than pulling a single power plug feeding an entire equipment rack (such as your UPS).
Powering multiple devices on at the same time can create a situation known as “current-rush”, such that, a device consumes more amps (electricity) than it requires to normally operate. If you attempt to power on multiple AV devices (especially audio power amplifiers), you can potentially trip the breaker for the electrical circuit your equipment is connected to.