Will the new PSU I bought (Look at my above post) be enough for a 6970, or possibly even a 6990? I want some headroom for everything lol.
The Seasonic M12II 620w (M12II-620 Bronze), with its +12 Volt continuous current rating of 48 Amps and with one 6 pin and one 6+2 pin PCI Express supplementary power connectors, is more than enough to power a system with a single Radeon HD 6970.
It's only a midrange (i.e. in terms of power capacity) power supply that doesn't have the two 8 pin PCI Express supplementary power connectors that are required by the Radeon HD 6990. It's not meant for powering multiple GPU systems.
The Seasonic M12II 620w (M12II-620 Bronze) only has a single +12 Volt rail despite what is shown on the power supply's label. There is no OCP on each of those 24A "rails" which just confirms that it is a single rail design.