Looking into an upgrade PNY GTX560 -> EVGA GTX670

Hello, not too long ago I put together my first PC - the specs are:
CPU: Intel i7 2600k (3.4ghz)
RAM:2*4gb DDR3
HDD: Samsung Spinpoint 1tb 7200rpm
SSD: M-4 Crucial 64gb
MB: Asus Maximus IV Gene-Z
PSU: Seasonic S12 Bronze 620watt
Case: NZXT Phantom (Full)
Current card: PNY GTX 560
-link- http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Card looking to upgrade to: EVGA GTX 670
-link- http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Since I am still new to building custom computers I used a calculator and did some research, most sites are saying that the 670 would have a power draw slightly less than that of the 560 - even under load. Does that seem correct? Would there be any problems with the power supply if I used this card?

Also, I am not very familiar with component standards: Would a PCI 3.0 card such as the 670 work correctly in the 2.0 slots that my motherboard has? My own research seemed to indicate that even 3.0 cards would not max out the capacity of a 2.0 slot. Could there/ would there be any other problems with this upgrade?

(And of course the Phantom case has plenty of room for the card to breathe)
(Running Windows 7 64-Bit)

Thank you for any and all answers and advice, it is all greatly appreciated.
P.S. If there are any issues or complications please specify, I'm attempting to learn about computers as well as build one, again thank you