i'm in desperate need of an APC backup power supply for my mac pro and acd. the old backup i've got (APC ES350) is not sufficient to power the mac pro and acd. i purchased the ES350 for my powerbook almost 7 years ago. anyway, every time i have a power failure (it happens quite often), my entire system shuts down. which APC should i buy? i want to ensure that everything still runs for a good while so i can save everything before powering down completely. thanks!!