Be a bit careful about buying through a group. Most of the "special offers" are a seller who is trying to beat Godox's rules on minimum pricing by selling off-book - a bit dodgy with a distinct possibility that Godox won't honour the warranty.
When it comes to power then yes, more is better - 200 W/s can only contribute to ambient light when it's bright, but could be useful in dull conditions. 500 W/s isn't really a measurable reduction from 600 W/s, specially when you factor in other factors such as system efficiency. And whether you actually need to overpower the sun or not will depend partly on whether or not you're a pro who needs to produce the required results regardless of the conditions - in other words, if you can choose only to shoot in less bright conditions then you can manage with less.
Another massive factor is distance, i.e. the ISL. If you can get your lights really close then there are massive improvements to the effects of the flash. And yet another is the choice of modifier - in the vast majority of situations there's no point in diffusing the light by using softboxes or umbrellas, that's mainly for indoor use. Use standard reflectors or high intensity reflectors instead
https://www.lencarta.com/all-products/light-shapers/lencarta-high-intensity-reflector-mod009 and once again there are massive gains in effective power.