Those server based PSU's are some of the most efficient it does depend on the power supply of course but they have to be due to fixed limits on power for servers when in datacentres and colocation.
I agree that maybe it has better sell on value than the modified one but I definately want to overclock and price for buying the hardware is bad in the UK, i know that the system can support 3 of them from one PSU but thats without overclocking, i dont know how much power extra is required per unit.