tkin
Back to school!!
The load rating in websites are a damn lie, look at my system, That APC 650VA UPS gives me 35-45mins backup(only system with minimal load-song playing, browsing, nothing else connected to it, have got separate UPS for monitor).^^no. 600VA won't be enough for a quadcore + GTX275 rig. to get a 15 minute backup, a 1kVA is absolutely necessary for that 650W PSU.
Also, a 650VA UPS has max power output capacity of 390 Watts. And this can give backup of 13.5 minutes for a load of 195 Watts.
A 1kVA UPS has max power output capacity of 670 Watts and gives 20.6 minutes backup if load is at 335 Watts.
*img26.imageshack.us/img26/2681/capture007w.png