If you're serious about it I would recommend going with MOTU Performer and Composer. I started using it on a Mac Plus in 1986 with an Apple MIDI interface which drove a Synclavier II and various tone boxes. MOTU was considered state of the art at the time for the Macintosh and for the technology, you will get the best results with it. The only difference between the Plus and SE is that the hard drive was built in. Otherwise the same limitations apply. Max out the RAM cause you'll need all of it to get as many voices as possible. The built-in Mac sound capabilities limits the number of voices you can have, but again if you are serious, you'll need outboard gear anyway. It uses a standard MIDI interface so voices are only limited by RAM and file size.