yes you need this
this tricks the psu into turning on.
http://www.ebay.com/itm/261302980079?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
then go to this guy
https://bitcointalksearch.org/topic/m.6783806
you will be far better off and you will spend less then70 bucks. you will be able to power 3 blades.
as cablez has 3 plugs 2 sets have 6 plugs.
I have all the gear you have and I have the better gear. night and day difference.
by the way your gear will pull 10 to 20 watts more as the psu you picked is under 80% more like 70%
you should reall get the cables by cablez