WaveWizard is useful when needing to resample the frequency of multi-channel Wave files (for instance, from 44.1 kHz 5.1-channel to 48 kHz 5.1 channel) while keeping the proper channel mapping headers so Aften can process them correctly.
I use Audio Converter Studio, it's not free, but I'm very pleased with it. I usually have to deal with many formats, and this tool supports a lot of most used audio extentions. Besides, it supports CDDB, and I don't have to type in the file info, it will be automatically downloaded from the internet.