Seeing as you're going unamped to an iPod, the M50s are the best bet. They're pretty much the default entry-level audiophile headphone, and cost about 150 USD. They run very well without an amp (though they are even more astounding with one) and will have you lusting after great sound like theirs in no time. The M50s are a tiny bit bassy for some users, but seeing as you're listening to Rock and Hip-Hop, that should not be a problem. I personally love my M50s, and I was in the same situation as you less than a year ago. I now have owned over a dozen headphones and earphones (most of them high-end), and the M50s are still second place on the list for their sheer unamped practicality. If you're not using an external amp, the M50s cannot be beat.