MM vs MC cartridge for ARC SP-4 pre-amp

I am considering either a new Denon, or low hours Grado Prestige MC cartridge. I currently have a MM cartridge run into a MAG input. There is a head amp input available on the SP-4. With an MC cartridge am I going to get the best performance out of purchasing a head amp? If so, can I get enhanced performance out of my MAG input with an MC cartridge and later upgrade to a head amp?