Yes, you need to have at least a PCIe x4 to get maximum advertised speeds of the SATA III SSD. But those cards are not cheap, look at the cheapest one from newegg for $70 http://www.newegg.com/Product/Product.aspx?Item=N82E16816115114&SortField=0&SummaryType=0&PageSize=10&SelectedRating=-1&VideoOnlyMark=False&IsFeedbackTab=true#scrollFullInfo,
and the three reviews are not good. As I know sometime it is not guarantee to work well.
My point is no worth that you put down that $$ for the card and just buy the SSD. Even your MB only has SATA II port then you are ready to get the SSD, and you will enjoy it.