I think for angelfish, water quailty is very very important.
Used to keep an emperor angelfish 3 years ago when i just started my first ever tank. Didn't read up much and added a emperor angelfish in, after a few days, its colour started to fade and in the end it died.
So yeah, i suggest to read up more about angelfish and let your water be more matured by then its safe to add a emperor angelfish.
Just my personal experience and opinion.