You probably should find out what kind of sound file the receiver's equipment can handle. If not mp3, then perhaps mono, 8-bit WAV? That would be a somewhat smaller file. AIFF has a couple of compression options. Any of the compression options or reduction to 8-bit would significantly reduce sound quality, as opposed to mp3 (at a bit-rate of 128 or above). See what your options are using the export function in QT Player. There are other export options in iTunes, for instance, but if the playback equipment won't handle mp3s, then I doubt it will play Apple Lossless or AAC, etc.
When you exported to mp3, did you use a typical bit-rate such as 128? Some devices can only play back a limited subset of bit-rates.
Sorry, by HTH I meant "hope this helps"