It's fine - PCIe (which I presume is what you meant to type) is completely backwards-compatible. In fact, a card like that wouldn't even have any speed difference between the two.
Oh, sorry, yes. Pci-e. "E" is very close to 3 on the keyboard ^^.
Tho i don't think i'll but that one, it's a little too expensive for me atm. I think i'll search one in the 50e-100e range (e = euros).