Could try this solution?
http://www.raidsonic.de/en/pages/pro...=2571#techdata
It does only take 2 drives, but they are stackable, takes 5.25 and optical as well.
Can be got at Scan
http://www.scan.co.uk/Products/Produ...roductID=81537
for £82 each. Get an Y-split power cable & only one power socket needed.