All UPS under $500 or so are of the "standby" variety which let AC power through under normal circumstances and don't do any cleaning aside from AVR buck/boost if your line voltage is under about 108V or over 130V.
For brownouts and other stuff, almost any UPS of sufficient output capacity to supply the worst-case power your system and attached peripherals should do. You'll likely be looking for something rated 1300VA or better if you want 10 minutes of backup under worst-case load.