Regarding the Sennheiser HME 45, we get them company provided (without ANR except a few fortunate ones) and i dont think its a very reliable headset, im on my 4th in 6 years now so i wouldnt even think about spending cash on it. Another thing is that i get a headache after a few hours since the ear-parts are pretty hard and the pressure on your ear especially if wearing glasses is pretty high and tends to be uncomfortable after a while.
Used the HME 25 during my training and it was a very comfortable headset with great noise reduction (used it on Senecas and Cheyenne), however it is a closed cup so it is a bit harder to hear or talk with someone outside of the intercom circuit (for example the girls serving the coffee).
Btw, both models are available for the normal 2 pin connectors still with ANR circuitry but need a small battery box in the line then and you have to keep the batteries loaded on your own.
Was not fortunate enough to test the Telex 850ANR yet (hopefully someone at the ILA has one for test) but it does intrigue me with soft earpads, open cup and ANR circuit without the need for a battery box on a 2 pin assembly.