There are some UPS units that are capable of supplying an entire office computer center for a period of time. Of course these things are huge...the one I've seen was the size of a small car....at work (one weekend when they were being replaced).
Instead of putting your whole house on a UPS, why not just hook up the sensitive electronic stuff to one, that way if there is a brownout, it gives you time to properly shut everything down...the lightbulbs can deal with reduced voltage.
