I have now added a second modular PSU to the dual Opteron 165 simulator rig – making it a smidgen over 1kW (Hiper 580 + new Corsair 450). The Hiper is primary (as it was there first) and drives the Corsair at start-up via dual PSU coupling I found in my kit box (must be from the Hiper, but not sure). There are instructions on the interweb on how to make or where to buy these from – but a very handy little cable.