I have an old iMAC C2D 24 inch 3.06 GHz 4GB RAM. How does it compare to the i7 4GB RAM 11" MBA concerning calculating power ????? I am using the iMAC now for FCS but rendering takes ages (>24 hours for a 1.5 hour project). Does the MBA do a faster job ?? I want to combine the MBA with a 27" screen so I have real estate at home and portabality on the go.