- The Seasonic S12II 620 is apparently a slightly updated S12II design called 'S12II Bronze'. Reviews look good. The 520W version is also from this newer S12II Bronze series :
Seasonic S12 II Bronze 520W Review .
How much are you getting it for?
- The Antec TP-650 is based off the better Seasonic M12D design. However ripple on both this and the earlier S12II Bronze seem to stay within <25mV, so both seem fine.
- The Corsair TX650 is a tweaked S12II design. Yes it is a slightly dated design, but its not bad.
Pick whichever one has good support in your area.
- The Seasonic SS-750JS looks to be a budget design just below the S12II, so you might as well get the S12II itself.
The SS-850AT is a different series and a different story - its what the newer Corsair TX V2s are based on. But obviously its overkill for your needs, unless you're able to find a Corsair TX V2 here.