Mark1234
I confess, that apart from being tight, one of the reasons I'm not sporting an ANR headset is that I worry about hearing protection - there are plenty of frequencies outside the ANR coverage, and the passive attenuation of the X at least wasn't great.
The 'traditional' DC's, plus in noisy aircraft earplugs and turning the radio volume up work for me - though not as pretty and probably less comfy. I've alos pondered that my rather nice inner-ear-monitors I use with the ipod might go nicely under the regular headset, and they're about 40db isolation in their own right..
My concerns too and the Bose X has been analysed by my employer and was found wanting (albeit in an extremely high noise environment). I too have tried earplugs and turning the volume up, but that increases the noise energy in the earcups - a bit counter productive. I also suspect that it causes hearing damage in the band of frequencies associated with the human voice. CEP-USA (no connection) do a foam earplug with a tiny speaker inside which you plug into you existing headset (after a bit of DIY fitting) -a bit like the in ear monitors you get for mp3 players. They claim a minimum of 30dB at the lower frequencies, increasing at higher frequencies. The result is much clearer coms (due to the quality of the speaker), a fantastic noise attenuation of around 50dB total, comfortable for long periods, reduced fatigue all for around US$100. They are so good, the US military issue them to all their helicopter pilots.