Go for it, they are an awesome angel!
A Goldflake over 6" is a risk though, as they may be hard to acclimate to captive food. I just added a 2.5" sub-adult with juvi coloration (paid $200) from QT to a tank of existing angels with zero issues. Although I had to completely tear apart my rockwork, let it sit looking a mess for about a week. Then I restructured everything and there was zero aggression. If you cant do that, go with eggcrate divider for 2-4 weeks until the Emp gets used to the GF.