UPS power is not cheap. You might be best served to figure out what you absolutely can not live without in the case of a power outage. Plug that stuff all into one power strip and buy one of those kill-o-watt meters to figure out what your power usage is for those devices. You can then go to a ups manufacturers web site like APC for example (my choice). They pretty much all have calculators that will tell you how long you can supply that load with each model... Then get the plastic out!
"...but the guy at the LFS said I needed it!"