As of late, I bounce back and forth between pronunciations of Magus and Janus.
Janus can be 'JAH-nus', 'IA-nus' (as in the Roman god of doors; they have no J), and 'ICK-el MAY-gus'.
Magus is almost always, though, 'MAY-gus', but sometimes I go all Roman with his name and call him 'MAH-gus', where 'gus' is more like 'goos'.
And for Marle... it's Marl. That's it. That's how they do it in Japan, yes? Besides, Marlee sounds wrong. I almost always turn that into Marlene.