If I were you, get the Dave Clark for now. You'll probably use them for a while, if you're worried about the hearing aspect, do what I did for years and cut an ear plug in half and use them as well as the DCs.
DCs are perfect for the bush environment you'll find yourself in.
I was very underwhelmed with the Telex's.
I have a different pair of Sennheisers but their ear pieces began to peel after 5 years.
The Bose are great but I am not too sure how they'll go in the tough bush environment.
My DCs copped a beating. Searing heat and dust. Lots of vibration and general hard abuse. They were dropped and (accidentally) kicked more than once. Tough as nails. They're 20 years old and still work just fine.
When you're working and have an idea about where you're heading, flog them and buy the Bose A20s. (Tax deduction)