Cyberpower 1500VA Pure Sinewave Battery Backup UPS for $120 with free shipping.
We have one protecting our computers, and believe it's one of the best battery backup units on the market today.
The pure-sinewave ensures battery power will be as pure as possible, keeping your electronics protected.
Here is a video showing the power quality output.
Basically, anything that has a circuit board (computers, TVs, DVRs, hard drives, etc) could die when electricity fluctuates, and this model tries to make sure that never happens.
This 1500VA is big and heavy, capable of 10-30 min battery protection for a fileserver or desktop PC, cable modem, and monitor during a brown-out or power outage.
Oh, and this model is rarely found for under $175, and normally sold for $200 to $215.