It may be a little bit of work, but the best device I know of is to get a clamp-on ammeter (it has jaws that form a hollow circle), take the cover off your breaker panel, and then clamp the meter around the hot wire from each breaker to measure the current in amps on each circuit while stuff is powered on.
As you're probably aware, it's nice to have a little bit of extra current "margin" on the circuit so that you can plug in something else temporarily without blowing the breaker.
You may have to install new circuits that are dedicated to the computers and other equipment. If you do that, Leviton makes a very nice "Whole house" surge suppressor that can be attached to your breaker panel. It would provide some good surge protection for about $150 for every electric device in the house. Then you don't have to buy surge suppressors for every item in the house that you want to protect...It takes a bit of work to install it, but it is worth it...
Randy
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Happy owner of 2 Centrals, 2 Empegs Mk2a 160GB, 1 Empeg Mk2a 60 GB, a Rio Riot, 4 Rio Receivers, and two 1GB iPod Shuffles...