Question regarding UPS. On a MacPro 3.2Ghz configured with.. 20Gb Ram, 5TB HD's, RAID card and ATI 3870 with the optional 30" ACD. How does one workout what rating of an UPS is required? I know a 1500VA is suitable but how long is the running time? 10~15mins? Is there anyway to measure the amount of energy my system is consuming?