both have similar power on their 12v rail (38-40a) have solid reviews for their price points. the OCZ ZS offers a bit more efficiency but nothing major over the CX600. both are good choices for budget units.
as for SLI/CF, unless you plan to run dual AMD 5770 or something similar in power demands, I would get a PSU with a bit more power. What video cards to you plan to purchase?