I wanted the most effective noise cnacelling headset about - and I imagined the new BOSE X-Headset might be the go. I was pretty happy with it until another pilot let me try his David Clark H10-56X.
The David Clark is heavier and bulkier, but is superior in noise attenuation. Also, when the batteries fail - the David Clark is a very effective passive headset. The BOSE sounds terrible - let me tell you - you scramble to get new batteries in ASAP!!! SO, for value for money AND better attenuation - go for the David Clark. I was in Yemen and I couldn't get the BOSE back to the factory or I would have exercised the 30 day moneyback guarantee... also - the battery only lasts half of the published time span - about 10 hours.
Cheers,
Ed