Quick recommendation for a brand I didn't see mentioned. I've had a great experience with CyberPower. The UPS I picked not only gives me a good half-hour of running time when the power goes out, it even has a detailed status display (multiple screens that include estimated running time remaining). It's built right into the box so you can activate the display without having to have the computer running. They have software installs designed for Windows, Macs or Linux.
With a MSRP of about $130 for models like the one pictured, it's definitely not outrageous for what you get. The manufacturer's website
even has a design page ("sizing tool") that lets you match your setup to one of their models. I really love that you can disable alarms so the unit just quietly does its thing, and if the outage lasts too long it'll gracefully shut down Windows. (Probably something similar for the other OS flavors as well.)
I snagged the pics below from their site -- click to enlarge. FWIW, the above is based on my experience with the CP1500C which runs over $200 retail. On-demand (quiet) fan cooling rounds out the features for my model.