SgtGiraffe
Legendary Skial King
I read that there won't really be a noticible differenceIt is backwards compatible, but you will not see a big increase in performance due to the slot or possibly the cpu not being able to read the speed of the 3.0. It will run at the speed of the 2.0 slot.
http://www.overclock.net/t/1267838/using-a-pci-e-3-0-in-a-2-0-slot
http://www.tomshardware.com/forum/344877-33-will-express-card-work-slot