You still have to wear a headset below 180 with a boom mic. A hot mic system would still be very nice so you didn't have a half clamp that is piping a loud voice into one ear with cockpit noise in the other. Most of the hearing loss actually comes from the ear with the headset because you have to turn the volume up louder than normal to hear it over the rest of the noise in the cockpit. The 757 might be quiet, but a hot mike would still be alot nicer than no hot mic.