This will be one of those threads where everyone lists what they have. I'll probably do the same, as I was in your same place a month or so ago, looking in the darkfor a nice sounding headphone for not too much price. Along the way I learned a great deal from the members here as well as reading some reviews. First thing I learned was that there are different types of headphones, open back, closed back, on ear, over ear etc. Since I already own a pair of closed back, and the principal use for my new pair didn't require any sort of blocking out sound from around the room.. And I wanted a bit wider imaging and I read where open back can give you that. I went with open back.
The next thing I learned is that the impedance rating of a headphone makes a big difference in what headphone amp will handle without making changes to frequency response. Called impedance matching, you want the output impedance of the HP amp to be around 1/8 of the impedance rating of the headphones. If the headphone impedance is 50 ohm, you want a amp rated at around 6 ohm or so.
http://nwavguy.blogspot.com/2011/02/headphone-amp-impedance.html
What I ended up buying was the
Sennheiser HD 579 and am very impressed with their sound. The depth of the sound stage is really something I wasn't quite prepared for and while not a bass heavy phone, has plenty of deep quality (not muddy) sound to it for me.. I highly recommend this one if you decide an open back entry level phone is right for you. Of course there are so many to choose from you will just have to read the reviews, and if you can narrow it down and go listen to some you will get what you want..