So you will need a portmultiplied enclosure as well.
As far as I know ATTO nor Rocketraid make express34 cards.
There is a prepackaged solution from Caldigit called the HDOne. That allows raided editing on a MacPro or MacBook Pro as the raid controller is in the drive case itself and not residing on the card and Caldigit makes a proprietary card for both the MacPro and Macbook Pro:
http://www.caldigit.com/HDOne/hdone_mobility.html
Jeremy