your PCI ex is 2.0 (not sure if it can handle 3.0) but if it does don't expect to work at full specs.
there plenty of 2.0 cards that will work though.
It just depends on what are you looking for.
I have a similar situation so when I upgraded I just choose an Nvidia GTX 560 ... (2GB GDDR5)
I know is an "old card" but for me it works!
I play games like Tomb Raider 2013 and others with very high settings with no problem. (I also have 12 GB DDR3 RAM)
(your motherboard can handle 32 GB of RAM) so you shouldn't have any problems.