Kozykeys:
The mini disk recorder is indeed a great way to record your live performances on the gig because it is so small and convenient to operate on the fly (I got an Aiwa AM-C80). Still, the minidisk is a 'compressed' format, so won't match the CD or better quality which 16 bit or 24 bit/96 khz provides. To achieve real pro quality results, you need capture the most you can on input.

NSR: Btw, for recording vocals, I strongly suggest using a good quality 'condenser type' mic. A dynamic type mic (Shure SM58/EV757, etc) is fine for live performance because it is rugged and can withstand the riggers of the road/stage, but a condenser mic (though more easily damaged if dropped) will capture the vocal clarity & detail which can't be reproduced on a dynamic mic. I own and highly recommend the AKG C3000 for its exceptional sound and sound, as well as its excellent value (for the dollar).
http://www.akg-acoustics.com/english/microphones/index.html