Gtx 470 Nvidia and Gtx 260 Palit

Hello,
I am curious about installing another graphic card to my rig. my rig already has a GeForce GTX 470 from EVGA. Now can I install a second GTX 260 graphic card from Palit maybe as physx. I know my rig has an igpu from Intel and virtu software installed. By the way It's custom PC assembly by me, motherboard is an Asus p8z68-V/GEN3, GeForce GTX 470 graphic card from EVGA, 16GB of DDR3 Memory, an Intel Core i7 2600k cpu, Hydro Series 80 Cooling, 1TB WD Hardrive, and Windows 7 Ultimate 64Bit OS, all this are in a Rosewill Thor v2 Full tower case, and 1000w Rosewill power supply. I will appreciated any advise or help you may provide. Thanks in advance.