Trying to stay around or under $200.
No amp and mainly will be used for ipod.
I listen to alternative rock, prog rock, electronic such as psy trance.
Also rap and hip hop.
From the reading I've done on head-fi, I'd go with the M50's, they don't need an amp and are supposed to be good for lots of different music. But there's no definitive answer (and also I don't own those so I don't have my own opinion to offer). You should ask this at head-fi, it's a forum of all audiophiles.