The SeaSonic SS-600ET Active PFC is an OEM power supply and is sold to system integrators in lots of ten.
It's based on exactly the same platform as the SeaSonic S12II Bronze Series and has the same internal components. The SS-600ET Active PFC shows its OEM intentions by not having any sleeved cables.
The OCZ ZS Series 650W (OCZ-ZS650W) is a retail unit made by Sirtec. Hardware Secrets gives it a good review.