Isn't there two schools of thought on single vs multiple drivers?
Single driver headphone or multi driver IEM?
That's a very generalized discussion. Physics will explain why it's best to have at least 2 drivers, a low driver and a high driver in an audio speaker system. The dynamics to reproduce highs and lows dictate different materials and construction to reproduce them accurately. Of course, you can have a really good single-driver and a really lousy multiple driver, ad nauseam. That doesn't negate the physics involved.
And while I think the folks at head-fi.org are smart folks, I've never seen a discussion on the performance aspect of headphones and IEMs. It's one thing to sit in a comfortable chair and listen to music. It's something else to play music, listen to the rest of the band and singers, and the needs that live playing dictate. I'm not saying that they aren't qualified to speak on headphones, but I din't see where they share our experiences.
I spent nearly $600 on custom-molded IEMs. I've since tried, for various reasons, tried some of the less-expensive models that get discussed here and with varied results. Obviously, custom molds are easier to get a good seal with, so I hesitate to rate less-expensive models on that basis (in fact, the Westone UM30s are VERY impressive and I have a set of those as a spare set of IEMs).
I'll just say that my decision to go with the $600 IEMs (In this case, the 1964 Quads) was a good one and I'll never, ever regret it. I'll never assert that buying anything less is a waste of time, only that the caveat of getting what you pay for applies very much here (and it goes without saying that not everyone needs to drive a Porsche...

)
However, by the same token, I'll not tolerate being told that I wasted money on a set of IEMs driven by marketing and snob-appeal from anyone.