Sensible audio settings
 

Although I have had an EX1 since February I have not really addressed the audio side of the camera, having shot B-roll mute pictures till now it has come as a surprise to have to do more than plug in a mic, headphones and shoot. I am monitoring on Sony MDR-7506 cans and getting a low level signal even on the highest monitoring setting. I am going to use ECM-77 mics for interviews on -55db setting and 416 on -38db to avoid distortion, mics are powered by the camera's internal 48volt supply. Sound seems clean apart from hiss that presumably comes from the headphone amp - is this a good set up?

Your settings don't sound too far off to me. My Sennheiser MKH60 shotgun sounds fine around -50dB on the manu setting so you might want to bump up your 416 slightly. That's with the external level control set to 5 which is basically the centerpoint (neither cut nor gained up). Not sure why you are getting such low levels overall, though.