The problem with power supplies is that when they fail, if they fail, spectacularly, they take other components with them (graphic cards, motherboard, RAM, CPUs, etc...). These are the things the warranty does not cover. Of the three possible units, I'd toss out the ThermalTake unit. It's really a tough call between the used Seasonic and the new Corsair.
The Seasonic is going to have better protection so if it fails, it's less likely to harm any of your other components, Also it has the extra headroom so it's not like it's being pushed that hard when running your RX 570.
The Corsair has the advantage in that it's new and it also comes with the three year warranty. The down side is that it's at the lower end of the recommended power requirement for your graphics card. There's no extra headroom. This isn't really a problem as the recommendations are typically overstated and are for the whole system anyway, but I still like having the extra head room,
Ask the seller if he'd be willing to extend the warranty for the Seasonic to six months. He'll probably say "no", but there's no harm in asking. If, on the off chance he says, "Yes", you have your winner and get the Seasonic. If not, go with the new Corsair.
-Wolf sends