Will the Trust  1300VA  600watt output  ups be ok for my xps630.  It is for sale here.     

http://ecomm.euro.dell.com/dellstore/basket.aspx?c=uk&cs=ukbsdt1&l=en&s=bsd&itemtype=SNA&oid=3547154a-451e-43b0-aa98-a9a6601e8f5f

I have removed the two ATI HD 3870 cards and replaced them with one HD 5850 so the power usage of my PC has dropped accordingly. ( the 5800 series use a lot less power than the older cards)  Surely 600 watts will be enough to keep my PC going for a short time so that I can shut it down properly in the event of a powercut.

Informed opinions sought