I'm thinking of buying some IEMs to go with my X3 and I am a complete newbie, plus I have very little chance to audition any gear. My target budget is £150 (about the same as the X3 cost for non-UK head-fiers).
I'm not a bass-head but one of the first things I look for is "well-defined" bass. By that I mean I listen to a lot of music which features acoustic bass and I like to be able to hear and maybe even isolate the sound of the bass, especially when plucked.
The next thing I look for is directionality (i.e. being able to clearly detect the direction a particular instrument is in the mix).
Finally, my ears are a little old so a little bit of extra treble probably wouldn't hurt, but I'd prefer detail to volume (same as I tried to describe for bass, really) but this is much less important than the other criteria.
As I said, I'm a complete newbie, so I'm not sure if what I've tried to describe makes sense, but if anyone with more experience has any recommendations, I'd love to hear them. I currently have my eyes (ears) on a pair of Sony XBA-30s but maybe they would be a little too warm with the X3? (I know warmth is relative but, as a guide in my case, the X3 is already warm enough for me with my current 'phones - Sennheiser PXC 310s - a little extra warmth would be okay if I get some extra detail to go with it). According to my research the XBAs aren't that warm with a low-impedance source...but I could have misinterpreted something...but that is why I'm still considering them, plus the prices for them look pretty good ATM.
Just checked the definition of Warmth in the glossary. It turns out that some warmth is maybe what I want (but not the "excessive" bit):
But I think when I said that I like detail in the bass, I'm actually looking for the harmonics, as well. As I said: "Newbie", so feel free to correct me...