My sound experience has been like this: I used to just listen to music on a pair of those sony ear clip type earbuds. They sounded more or less fine to me. Then I started listening through my dad's Koss over-ear headphones. They were retailing for about 60-80USB back in the day when he bought them, but they were worth about 40 when I started listening to them. Immediately, I noticed a difference. I loved how rich and mellow the sound was. They had crystal clear bass (compared to those earbuds, mind you), and the treble wasnt all that bad. I was listening to bands like pink floyd, led zeppelin, system of a down, etc through them.
After those broke I finally started looking into some different head gear. I settled on the Koss Sparkplugs because they were only 11 bucks and had "sickening bass". Well they sounded fine in the bass department and since I mostly used them to listen to my PSP and not ever actually any music, they did the job rather nicely. They broke within the year though. 11 bucks only gets you so far. After a while I started looking into high quality audio and seeing what people were using. Shure was getting a lot of hype at the time and I was still new at the whole research thing. I figured price and quality are directly proportional and thats all there is to it.
I made my biggest mistake of a purchase with Shure E3C headphones from the apple store. They had absolutely no bass and though they had a very high quality cable that near eliminated microphonics when they were worn over the ear, I couldnt like them. At the time my music was almost exclusively 192kbps mp3's. If there was anything below 256kbps, howevr, the shure's let me know about it by reproducing the sound so accurately that all I could concentrate on was the cracks, whistles, buzzes, and all sorts of audio artifacts. Pretty soon I was back to using those 11 dollar Koss because I couldnt stand the complete lack of bass and absurd accuracy of mid/treble reproduction.
I stumbled across Creative EP-630's, and they offered me a really nice blend of bass, treble, and mid range sound and for the last 3 years that has been enough. But now I'm going through that musical metamorphosis where old teeny pop music just doesnt soudn worth listening to and talent/good mixing becomes a prerequisite. The only songs I've been able to keep listening to without getting annoyed at the mood of the music are by radiohead, pink floyd, and Muse. Sure, system of a down is still there but they mixed their music so abysmally that I can hear the distortion through all but the crappiest of headphones. Even my car's speakers cant ignore the distortion of the original mix. I bought the bose after a while simply because I had some cash burning a hole through my pocket and i was a young idiot. I had experience with the bose sound and it sounded way better than those ep-630's. Much faster response, much clearer in any range, and unlike the ep630's they stepped off on the bass just slightly so that everything was balanced. In the 630's the bass was, at times, overpowering.
So now I know a few things about my preferences listening to the Boss. I like crystal clarity in the bass range, I like sound reproduction that is relatively flat. By this I mean if you were to pump an increasing sine wave through the phones from 6hz-19khz, you would get the same amplitude of sound across the board (assuming the input wave was the same amplitude). I like the driver being able to pump out many notes per second without any of the notes bleeding into one another. I like an extremely wide soundstage so that, depending on the mix, I can either feel like i'm standing there watching the band record or so that the sound is able to get in front, behind, above, and right in the middle of my head with different sounds. The bose does this nicely, they are balanced a little bit forwards and do a complete crap job of playing sound in front and behind the head, but anything sound in line with the ears can be played/felt either right in the middle of the brain, or along the top of my skull. I do love the bose ability to play subsonics too, though I'm not expecting that out of an IEM driver. I hate that high pitched hissing/tssss sound, and I also dont like it when the sound doesnt go loud enough on my android device to do the music justice. On the bose, its like walking a tightrope. If the phone is set to max volume I'm good, but if the phone goes even a little less then the music suddenly sounds like crap. Random notes sound louder/softer than others, some instruments disappear altogether with the bose on lower volumes....
I definately wanted something comfortable enough to wear to bed and inexpensive enough to not worry about screwing up at the gym. I would never take a pair of Ultimate Ears Reference series with me and work out with those on....I found a pair of westone UM1's for about 150, same with a set of UE Triple.Fi. The thing with money is, I figure consumer benchmark for price of headphones is set to about 30 bucks for a "decent" pair. If that pair lasts about a year, you get your money's worth in terms of longevity. So basically I take the price of what I'm buying, divide by 30, and expect them to last about that many years with rigorous, daily use. The Shures didnt last me more than 9 months. The creatives last for about a year each before starting to sound a bit crappy, having the silicon slide right out of the ear, etc. the bose are nearing the end of their lives, but for 35 bucks I can refresh the pads, which are the only broken parts on them thus far. The driver stll sounds nice, though I'm expecting them to break hardcore before the year is over. That is why I'm trying to get a set of nice headphones that will last me another 2-3 years or so before having to buy another set. I'm not looking at Amps any time soon. If nothing else, i'll have my own desktop sound card by then. I plan to let the desktop be a giant media PC, capable of pumping out blu-ray, watching tv in HD, etc, and I dont think i'll be needing a seperate amp with it just to listen to music. If nothing else i'll have it pumping sound AND video via hdmi to a nice amp/reciever combo, and just plug giant headphones into that amp IF I have to.