When saving in Sound Forge, you should be choosing "Wave (Microsoft) (*.wav)" as opposed to several other WAV options, and setting the sample rate and word size according to what the sound was originally recorded at. If you've done that, there isn't an issue with playback due to the WAV format.
Have you checked the monitoring path from the HD24? How are you hearing the HD24 (compared to the files via Sound Forge)?
(ie, maybe the sound is distoring in Sound Forge, but the way you're monitoring there doesn't let you hear it?)