(EDIT: After more extensive testing under different circumstances (amount of sleep, amount of substance that might alter hearing such as caffeine, time of the day, wider range of music, more extensive EQ tweaking), I sadly have to recant my previous glowing praise of the W60. Below is now the edited version that reflects my current and more careful assessment of the W60.)
Westone W60 finally arrived, and during my early listening and testing sessions, due to various factors (amount of rest, amount of caffeine, time of day, music selection) I initially though it was pretty much EXACTLY what I've been searching for. But now after more extensive testing, it's clear that's not the case.
The "Westone house sound" of too much upper-bass bloat is still there, and there's an annoying peak at around the 10 KHz region (centered at roughly 9500 Hz). There's also two dips in the mids and upper-mids--one at around 2400 Hz and one at around 4750 Hz.
Those two dips aren't as problematic, but that pesky peak at around 10 KHz can be bothersome to people who are sensitive to that fatiguing tizzy treble on music that's mastered on the bright side. The bass bloat centered at around 150 Hz can muddy up songs what have lots of low frequency energy, but on songs that are relatively lean to begin with, will add more punch and warmth. I personally prefer neutral/accurate so I can hear exactly what the mastering engineer and music artist wanted me to hear, so I dislike any distinct coloration.
This the EQ curve I came up with to get the W60 to sound as neutral as possible:
With that EQ curve, a log sweep test tone is about as smooth as I could possibly make it, and it's really damn smooth. Those of you who have the W60, try that EQ curve and you'll hear for yourself how smooth the log sweep sounds, and how neutral/accurate your music now sounds.
So what does this new assessment of the W60 mean for my mission to find the ideal IEM? I'm not sure at this point. If none of these expensive TOTL IEMs end up being ideal, I might end up giving up on them and go for the cheaper options, since they're likely to be about as close (or far) away from neutrality as these so-called flagship IEMs, and if I'm going to have to EQ them anyway, I might as well just do it on a cheaper IEM and save my money.
Currently, the Hifiman RE600S comes the closest to matching that profile, since it's at least not offensive when not EQ'd, but becomes ideal when it's EQ'd. I'll likely try the RE400 instead since it's supposed to sound extremely similar but much cheaper.
I could also give the 1964 U5 a shot too. We'll see. I'm going to keep testing so I can be sure I've exhausted all scenarios to make sure I'm being as objective as possible and there are no variables left skewing my results.
...
I did also receive the Oppo HA-2, and while I think the product looks beautiful and I have no complaints about its features or performance (that very faint noise floor doesn't bother me at all--it's barely noticeable on low gain setting when using sensitive IEMs with impedance down to 16 Ohm), I'm not really sold on its necessity. Although I can't find any information on the exact impedance of my Galaxy Note 3, it's low enough that when I compare what I hear straight out of it versus what I hear from the HA-2, there really isn't any noticeable difference (when using very sensitive 16 Ohm IEMs like the Angie, with impedance down to much lower than 16 Ohm at around 4 KHz), which tells me Note 3's impedance is low enough to not be an issue for even the most sensitive IEMs. That means adding an external amp/DAC is total overkill because Samsung's already using very high quality DACs in their flagship products.
However, if I want to use my IEMs on my computer, or with my speaker/headphone controller (such as the Samson C-Control or any other similar pro audio monitor/headphone controllers), then I do need a very low impedance amp, otherwise the frequency response of the sensitive IEMs will change. The W60 has an impedance of 25 Ohms, but that is not linear across the frequency range, so even if your device can handle exactly down to 25 Ohm, you will still get noticeable dip in the mid to upper-mid region, as well as a noticeable rise from 8 KHz and on, skewing that beautiful neutral sound. The HA-2 is down to less than 1 Ohm, so it handles the W60 just fine (as well as all the other IEMs I have, including the Angie). So I think for the sake of flexibility, if I ever want to use the W60 on any devices that isn't low enough in impedance, I should have at least one amp that's very low in impedance.
I ordered a Massdrop O2+ODAC not long ago, because I needed at least one very low impedance reference quality amp (though I'm not as concerned about the DAC, since all the DACs I'm currently using on my sound cards, audio interfaces, and mobile devices are plenty good enough). The O2+ODAC won't arrive for a couple more weeks, and I ordered it before I ran into the impedance mismatch problem with the Angie, which is why I ordered the HA-2 to address the problem immediately, and also I thought having a small portable amp would be a good idea.
I'm now wondering if I should keep both the HA-2 and the O2+ODAC. I seriously doubt I'm going to hear any noticeable difference between the two. Both are about the same in impedance level (less than 1 Ohm), and both have high quality DACs. I think the O2+ODAC is amazing bang for the buck (especially the Massdrop version), but the HA-2 is more versatile due to its portable form factor, so that if I'm traveling and using a mobile device that doesn't have low enough impedance (such as a laptop/2-in-1 hybrid), I only need to bring the smaller HA-2 and can use its battery power, instead of the bigger O2+ODAC that needs to have the power plugged in. I'll have to decide soon since the HA-2 has a 30-day satisfaction guarantee.
My ears are kept exceptionally clean at all times, which might be way I have such a hard time with that 7KHz peak resonance, since my ear canals always have plenty of space for that resonance.
