Headphones / mic combination like DO6BJ shows is so much better than anything from Heil, in my opinion which of course is not universally held. To me though, having used a Heil headset for 25 years until recently, it is a myth that they are the best. People get carried away with the hype and end up paying a (hefty) price too.
When I changed to Expert Electronics radios, the best audio via Heil came from an IC insert and the electret input. But this was improved on considerably by the ModMic which I now use. The transmit audio can be tailored for rag-chewing or DXing and the gain is more than sufficient. Similarly, other headsets beat Heil for audio response and comfortable wearing. The AKG 240 is a good example. I have the Audio Technica ATH-M50x - my Heil ProSet is now gathering dust in a cupboard.
Erik EI4KF / G0CGL