I love my Mach 1s. Converted over from the Bose, and never looked back. They work GREAT in the ERJ, with custom ear molds. The ear piece does take some practice to figure out, but it comes with time. I've also never had a heating problem due to impedance differences. I think only the CVR output is 600 ohms. And my CP laughed at me when I asked him about the TSO thing a while back and said it's not an issue at all.