Maybe SoundFX (or SFX): http://aminet.net/package/mus/edit/sfx-bin_60m
As a registered user from bitd, I recommend this one although it's a bit technical and it's UI may take a bit to get used to, but it is one of the best there is. Soundprobe was good too, I can't recall how many formats it opened and the current status of availability, But if Stefan Kost is still supporting SoundFX I would give him a shout, SoundFX would be a great candidate to have an OS4 native version of.
http://www.imn.htwk-leipzig.de/~kost/soundfx.html
