Only needs to power a HP ML115 G5, HP MicroServer, AirPort Extreme and a HP 1800-24G for a very short time.
Only needs to be good enough for monetary power outages. We keep having short power outages of less than 1 second, 2 last night within 5-10 mins, don't think it is doing my DC's much good. Happen about once a month.
I like the APC range from experience :-). Looking at a Back-UPS Pro range, prob a 550.