It's very quiet I only hear a slight humm but the room has to be totally silent which never happens.
I suppose you could try the re-home route but I would never do it because 1 I I would hate to have to get rid of a fish I've had for years and 2 I've read being in a tank that is too small can have biological effects on the fish even as a juvenile.
I wouldn't do a lion fish with a reef for small fish for the reason you stated.
Some colorful fish that would fit is the lemon peel angel or flame angel both are active swimmers and very colorful. They may eat coral though. There are dozens of wrasses you could get that are very colorful as well. There are a few smaller hogfish you could do also and anthias.