Spark LE Plus and Spark XL both support MP3 with the original Fraunhofer MPEG3 Codec. You can easily import and export MP3 files - and of course you have the full range of export options available. Spark LE Plus and Spark XL also support AAC (also known as MP4 or .m4a) via QuickTime.
Spark ME and Spark LE do not support these file formats.
Please note: the entire Spark line has been discontinued since March 2004.