First the machine! -> http://support.dell.com/support/edocs/systems/xps710/en/SM_EN/index.htm

Down that page it claims 750 or 1 KiloWatt dissipation which is "is calculated based upon the power supply wattage rating." But I'd still look at the PSU side panel and check those ratings.

This does have the usual PCIe x16 slot so that's not rare.

What's left is for you to check that PSU rating and mechanical clearances for your new video card.
Bob