Should NEVER replace anything with a level one anything. Level 4 guild > CoE or SOS level 1. At least make either one a level 2 if you intend to replace.
@ Star , it depends on what you want your build to be!! Do you want to be able to perform spy actions? Then get a couple SOS, but they effect over all plunder. If your early in your t4 quest. CoE is a great building, never did me wrong. So it's what you want yourself ,to be able to do