The David Clark X11 has a number of issues. biggest problem is they actually break. The plastic hinge that holds the earcup to the frame is breaking. The other main complaint is they seem to have insufficent volume even when all is turned up flat out but the biggest problem of all is David Clark will not allow any warrenty claims to be processed in Australia. All returns must be shipped back to the States for repair. Just rediculous. Imagine paying approx $1300 and having a problem a week later and being told it will be 3 months before you will have the headset back. Next one is the Bose. It has almost no passive noise reduction and if the battery goes flat or the circuitry fails you may as well take it off and use the speaker in the aircraft. Also the earcups are very shallow and they press on a lot of peoples ears which is quite uncomfortable. They have also had a major recall as they were flattening batteries in a few hours. The Lightspeed Zulu has become a real favourire and the Telex Stratus range has the highest nouse reduction around. Both have not had any real issues and the Zulu has bluetooth. Not sure about warrenty on the Lightspeed though as no real agent in OZ. Telex warranty definately ok in OZ. Another option is the David Clark H10-13 XL. Basically a H10-13.4 with a factory active kit fitted and not too expensive either. A great headset but not as fancy in the looks as the newer ones.