ReadyNAS Duo - UPS help needed

Hi, I'm a new ReadyNAS Duo owner looking to add a UPS into the system that will support a single PC, router & network switch & the NAS. I need the UPS to support a controlled shutdown if the power is not restored by the time the battery dies. From what I hear this is done via a USB connection, I've been looking at this APC unit; http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=BR900GI&total_watts=200&tab=models

- does anybody have any experience of this? Cheers