where do they sell power supplies like that? Is it dell? did it come with that board also? 
That's sidehack's breakout board. You can find out more here:
http://www.gekkoscience.com/products/D750_supply_breakout_board.html
I believe he is currently having a sale for these for like $55. You can find his thread in the groupbuy section. If he is out, minersource carries them also.