Have any of you actually looked at the spec?? The PSU is external; without reading the manual, who can give the correct answer?
I am guessing from what the OP has said, and the configuration of the stupid designer rig he owns, that he thinks he can run the 230w and the 180w in parallel (the case has inputs for both).
Even he doesnt know if the cards will fit inside, it looks like a sardine tin with the side off, so unless the card he has specified is physically smaller than what is already fitted, the answer is "no".
https://www.asus.com/uk/ROG-Republic-Of-Gamers/ROG_G20AJ/