Thank you to all the contributors here and in the IEM thread, you guys have assembled quite a horde of useful information for indecisive n00bs like me to parse through :D
I had been using the same model of headphones (earbuds) for over a decade - the Sony MDR-ED21LP. It got discontinued and so I've been looking for a replacement. I understood that the 16mm driver seemed to be what made that model so special, but I haven't even been able to find what size drivers are on most of the headphones I've seen in stores. I've tried Sennheiser CX 300 II, but I just cannot get used to them. They sound like a tin can. The Sony MDR-ED12LP "replacement" version of my beloved MDR-ED21LP were awful, AND they hurt my tiny ears. I also tried Sony XBA-1 but the sound on those just isn't as rich. Though the noise isolation is so good it's a bit scary.
The vast majority of music I listen to are live Pearl Jam concerts. These are official live recordings of a rock band. In addition to the 90s "grunge" music, Pearl Jam, RHCP, NIN, Soundgarden, I also listen to a little bit of "pop" music: Neon Trees, Awolnation, Arcade Fire, Third Eye Blind. Rounding out my tastes would be more mellow sounds like Van Morrison, Billy Joel, Mumford & Sons. I'd love recommendations for earbuds under $100. I came very very close to buying Monster Jamz headphones in a store because of the marketing on the box targeting "live music" but I really didn't want to be stuck with another pair of headphones I don't use (since I've already got 3 I'm not really happy with) so I've come here for some advice.