First off I just got done reading your build thread on RC. If it is in fact a 36x24x20 tank then its a 75 gallon, not a 80 gallon or a 100 gallon like you have posted. Second I have a 36x24x20 leemar tank just like that. Everything the guys above are saying is correct. As far as scratches go, just about every tank has them. They get scratches in moving and they get scratches when cleaning especially starphire.
Anyways I agree with your wife, throw more tangs in there. I had a yellow, powder brown, and clown tang in my 36x24x20 when it was set up. They will bicker just let them figure out their pecking order. IBTL and good luck.