Hi Thought id add my 2 pence worth...
Its worth doing a little research into each UPS before you buy.. they all work a little diffently... its to long to go into the main differences but
www.howstuffworks.com has a really good guide on the different ones.
i always suggest going for one that will shut your computer down not hibernate, my SmartUPS 1000v from APC does exactly that to the server just before the battery dies.. normally about 30 mins I found it usfull as we live in a shared house on key electric so the power goes a couple of times a week.....
Its worth rmebering that surge protectors do just that they dont protect against brown outs (a drop in electricity) in the sam way a line interactive ( i think thats what they are called) UPS does...
Have fun..