I'm wanting to purchase 2 UPS's possibly. The thing is I know very little about them. What size (in watts I think?) would I need to run the system in my sig? There are so many choices, I've seen from 200w to 900w for sale, I want to buy something that is plenty for my setup. One of my friends has a 300w UPS and said he cannot run his 21" monitor and his box on it at the same time, so this is why I'm posting this question to make sure I get what I need the first time!