In need of a new PSU

Hello, I am looking into upgrading my dell xps 8500 stock graphics card (Nvidia Gt 620 I believe) and wanting to put in a GIGABYTE GeForce GTX 670. http://www.newegg.ca/Product/Product.aspx?Item=N82E16814125466  I am aware they the regular 460w power supply will not support this new card so I am wondering what will? This is my first time doing any work to a computer so honestly i am not even sure if the graphics card I selected will fit the motherboard. Any suggestions will be greatly appreciated.