Dick,
I use a Sennheiser ANR in my Gentex SPH-5 and it works great. Because it's not aircraft-installed, I can carry it from ship to ship.
I was involved in some unofficial trials for it when I worked at Bell - we were concerned that it would interfere with hearing those 'odd' sounds that pilots use to figure out the world is about to go pear-shaped. It did not. As a matter of fact, it made any 'abnormal' noise stand out.
Some spark farmers wired up a power cable for me that plugs into the ship's Aux Power Cannon plug, which saves me carrying around batteries and such.
Awesome system, and I'd highly recommend it.