Yes, you do need a heatsink, tho that one is meant for a server setup...the case is small though, I think these will fit, but I would double check...think these give you 1 inch extra.
http://www.newegg.com/Product/Product.aspx?Item=N82E16835103166
and one more, about the same
http://www.newegg.com/Product/Product.aspx?Item=N82E16835150059
http://www.newegg.com/Product/Product.aspx?Item=N82E16835103166
and one more, about the same
http://www.newegg.com/Product/Product.aspx?Item=N82E16835150059