With the 20th anniversary of this station coming up in a few days, unfortunately I have to say that C91.3 has never had a particularly great logo:
…although if I really had to pick one, the original was probably the “best” saved by a vaguely local (well black, white and orange are used by a certain football team…) colour scheme.
Meanwhile in Melbourne, I found this from about Early 2001 during a recent look at old radio station websites via the archive.org Wayback Machine. Not 100% sure if 3AK actually used it as their logo or just as a website thing, but poorly designed either way IMO:
