I see Seagate & WD have announced these but I'm struggling to find many available to order. Only the WD Green one appears to be even offered as an internal option. What is more it is more expensive buying the internal drive than buying the external USB one. Has anyone bought one of these externals and stripped out the drive to put in their Mac Pro? I'm running out of space on my 1.5TB and swopping to 2TB hardly seems enough.