You can buy Uninterruptible Power Supplies (UPS) that have auto voltage regulation (AVR) built in. Look for something that will buck (cut down voltage if it gets too high) AND boost (bring voltage up if it gets too low). I have one for all my networking equipment. It provides surge protection as well, not quite sure how good but its there.
I would imagine getting a whole house surge suppressor and then a UPS with AVR for your more sensitive (and expensive) stuff might be the best idea. if possible, also look for one that outputs a pure sine wave. Square wave is cheaper but can possibly be damaging to electronics (not sure its been proven, and if it has it might not be an issue until well past the expected life of the device anyway)