I do not need extra "kick", as I listen mostly to classical, chamber, and the like. I use a Kenwood HD60GD9 on the road. Truth of timbre and coherence are essential to my ears.
Funny, I called Headroom yesterday, and the salesperson (let's call him Mr. Ed) seemed to emphasize my satisfaction with the ETY-4S and said that nothing could match them for natural timbre.
JVC FX700 (single dynamic driver) and Ortofon e-Q5 (single moving armature) would be excellent choices for classical, too. I concur that timbre and coherence are essential and prefer these phones to all dual and triple driver IEMs I've heard, including the CK10, CK100, SE530 and SM3.
james444, thank you very much for this excellent information. I will definitely followup. As much as I like my ETY4s, I feel like there must be something better for me to use on the airplane by now. When I finally get to the hotel room, I usually unpack my "roadies" and relax with wonderful music.
JackKontney, you are a gentleman, sir. Thank you very much for the pm's. I will be very happy if these leads guide me to the next step.