hmm. wierd. has all sorts of other things like usb3, yet no PCI-e 3.
my computer doesn't have usb3 but has PCI-e 3.

nevertheless, a PCI-e 3 card will work just fine in a 2 slot. You should realy try to put as much as you can into it but if you are seriously strapped for cash, consider this card then...
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130808it's double the price of the GT610, but it's faster ram speed and bandwidth size will be a great improvement. The GT610 you posted scores a passmark score of 342, while this GT630 with ddr5 scores a 719 the GT640 I linked before even with ddr3 scored 1302. this puts the GT630 right about in the middle...seems like good bang for the buck.
my videocard right now (9500GT) which scores 290 on the passmark (not much better than the GT610)... even with my overclocked FX8350, I might as well have a 486. "The herd is only as fast as the slowest animal" There are instances where I have had to dial back settings and reduce screen size to get frame-rates up to even 60 FPS.
I'm currently scabgrading my computer so i'm really lopsided. I'll be upgrading the water-cooling, then the power supply, then the videocard. once i get the videocard upgraded I won't have to worry about anything because the ridiculous bottleneck that is the videocard will be gone.