Canalphones and IEMs are generally synonymous. I'm not sure if the term "IEMs" is a subset of the more general term "canalphones" and implies a deeper fit, but that I wager is too technical for most consumer publications anyway.
Most lower-priced consumer canalphones are intended for younger listeners and for portable players, where they will be playing rap or rock. They're tuned to compensate for an mp3 player's typical brightness and to give the type of big boomy bass consumers prefer.
Once you get into higher-end canalphones, you won't have to deal with this. They're usually tuned to be a lot flatter. Professional canalphones are tuned pretty flat as well, though they're usually used with EQ, and portable players usually don't have any quality EQ worth mentioning.
Etys (ER-4P or ER-4S + amp) do sound like the answer for you, though I do have to warn you that they overhype the treble something fierce. I couldn't deal with it, though if you listen to primarily classical music, jazz, or ambient electronica, you probably won't mind an aggressive treble as much as if you listened to rock, metal, trance, and the like.
If you really are concerned about comfort, then custom molds are the answer. You don't need to get full custom molds, just a custom sleeve for the Etys or something of that nature would do. If you want to go full custom, the Livewires sound very attractive though I haven't heard them. I have the ES2 and I like it a lot, but I don't know if it's the sound you're after. It is very full, very lush and liquid sounding, flowing and organic. It's still very detailed and is fairly flat(ish) in frequency response but it could use some more treble extension and presence. For the money it's stellar, but I'd wager Livewires would be an even better value.
There's also the triple.fi stupid.name 10 pro, which doesn't go as deep into the ear canal as most traditional canalphones. It should sound pretty flat as well, though I wouldn't really know as it is one of the very, very few canalphones that I've never heard.
If you don't need the isolation, there's the Stax SR-001 system. I seriously doubt you'll find something that sounds even remotely as good for the money. It doesn't isolate and it requires you to carry the amp around, which itself will last about 2-5 hours on an average set of AA's (more on li-ion batteries). It has a warm full sound with some serious bass, but being an electrostat, it's a very tight bass and everything is very very detailed. It's a very different sound from most balanced armatures, much fuller and more headphone-like, though different from traditional dynamic headphones as well. It can be bloody uncomfortable, though.