I love the live presence I get from my analog stereo, but when I'm on the road, I have to resort to my iPod and earbuds. There are already many good Instructables that walk through custom fitting earbuds, and I recommend that as the first step toward portable live presence.
The one I used is:
With the exception of putting straws down my ears, this is pretty easy to follow. There may be others newer and better, so check around.
I use Sugru for mine. I feel that's the material of choice, but if you want to mix up your own goo, go right ahead. Also, make sure you only cover the OUTSIDE of the ear canal. You don't need to shove gobs of silicon down to your ear drum. The whole idea is to isolate the sound you want from the outside noise going on around you. Your ear is designed to funnel that noise into your ear canal, and if it gets that far, it's already too late to block it.
If you look at my earbuds, the Sugru ends where the metal part ends. The part that blocks the noise is the part having the increased surface area surrounding the outside of the ear canal.
Let me take a moment to explain what I mean by "live presence". Imagine you're at a live concert, sitting at the edge of the stage listening to your favorite band. Not only do you hear the sound, but you feel it as well. Not just the deep base, so popular at stoplights, but the click of the drummer's stick on the rim of the snare and the chords from the guitar at the instant they're strummed. All but the most muted and soft sounds effect your entire body, not only your ears. If your were able to reproduce that with perfect earbuds, all those pressures would still be running around inside your head, vibrating your skull at the music's frequencies and creating additional sounds even the totally deaf can "hear".
Speaking of which... I'm not a "spring chicken", as we old folks like to call ourselves. My hearing is poor, at best. I have to "fine tune" my music, to produce the same sound that you young people hear.
I think I've succeeded in this task, using a couple of apps available from the App Store (one free and one costing 99¢) and a unique earbud sealing technique that truly puts the sound pressure into my skull the same way sitting at the edge of the stage does in a live concert.