Can my computer support this upgrade?

Im just trying to see if my computer can support an upgrade to a SAPPHIRE 11197-03-CPO Radeon HD 7970 3GB 384-Bit GDDR5 PCI Express 3.0 Plug-in Card Graphic Card

If not, can you guys find me graphics cards that could be supported?

My budget is $250, on the graphics card. I already purchased a 600 watt power supply unit.

Or how about this: XFX Double D FX-787A-CDFC Radeon HD 7870 GHz Edition 2GB 256-Bit GDDR5 PCI Express 3.0 x16 HDCP Ready CrossFireX Support Video Card