Ace
Emperor
IMHO, KRC is a nice to have wonder if nothing better is available. It does add 20 points to your score and, assuming a size 10 city, on average, it will take only 30 turns to get your 300 shields back. I tend to look at 2 other factors here, 1: let the AI build it, while I build a more desirable wonder, or 2: occasionally, you will get HBR and/or the Wheel as starting techs which can make an early push for Explosives very attractive.
At the lower levels, where happiness is not as big a problem as on Diety, going for Engineering vs Monotheism is a better choice. You will get the extra shields for more turns to add to other wonders.
At the lower levels, where happiness is not as big a problem as on Diety, going for Engineering vs Monotheism is a better choice. You will get the extra shields for more turns to add to other wonders.