Honestly if you want to optimize for stability and speed I would ditch the MediaSonic Box and try to move the drives into the dell servers themselves. If the MediaSonic drives are 2.5 in it looks like the 7040s have an internal bay. For the 3040s it sounds like you are only using 1 of the 2 5.25in drive bays. I would say it's better to have 4 drives hooked up via pcie then 8 via eSATA. (got the drive data via dells website, might be different)