I'm curious to know if you ever replaced your Coppers? If so, what with?
I own a pair of Monster Turbine Coppers and haven't found much else that competes with them. I also own the Ety ER-4S/P and love the incredible sound isolation they provide (with Comply foam tips) for long-haul international flights. I've also owned two custom IEMs, but I only use the Etys on a plane. You'll never get the same isolation with a custom IEM that you will with the Etys + Comply foam. Your ear canals change shape and size too much over time for any CIEM to provide a consistent, comfortable seal that isolates like Comply foam does. However, long-haul flights are pretty much the only time I use my Etys, as their sound can be a bit dull and boring compared to that of the Monster Turbine Copper's. The Etys have the edge in the upper frequency range, but only by a tiny margin; the Coppers win in the low frequency range by a mile.
I've also previously owned the UE 900s and I doubt you'll think of these as an upgrade from the Coppers. Their sound is even more "neutral" than the Etys (hardly any bass at all) and they have a disastrous design flaw, with a detachable cable that will intermittently lose contact with the drivers. Even with DeoxIT contact cleaner, you've permanently got a tenuous electrical connection there. (Why was a rotating connector even necessary?) The other flaw I can't forgive with the UE 900 is the sound. It's just not that great, IMHO. Despite its four drivers, the sound isn't as good as either the Coppers or the Ety ER-4 and it distorts at medium-to-loud volumes. The UE 900 has much better ergonomics than its predecessor (Triplefi 10), but the UE 900 sound won't wow you like the Triplefi 10's sound might. Compared with your Coppers, the Triplefi 10 has a clearer treble, at the cost of a bit less bass, but I found the Triplefi 10's treble to be too harsh after prolonged use, so I still couldn't say I prefered these over the Coppers.
My recommendation would be to hunt down the tips that best fit you and your Copper Turbines. Try the foam supertips or the old, original, round gel supertips (avoid the newer, cylindrical-shaped gel tips as they don't fit anybody!). In terms of sound, Sony hybrid tips would be a very close second if you don't have any luck with the supertips.
Please let us know the conclusion to this story!
Edited by csglinux - 6/29/14 at 12:54pm