The ATH-M50 are definitely the pair of headphones that you're looking for. I've tried or owned a bunch of mid-fi closed headphones (Sennheiser HD 448, Shure SRH 440, the Beats, DENON AHD 1100), and i've never been as satisfied. The M50s are known for being high-quality, serious professional headphones that are also beefed up in the bass section. I honestly find the Beats to be way overpriced (atleast in terms of sound, I think the build quality, comfort, and design are all quite nice). The MSRP for the ATH-M50 is 200, they usually go for about 160, and you can often find them for around 120. I got mine at BH photo video.
If you don't like the look of the ATH-M50, I can definitely recommend the Denon AHD 1100.
The Shure 240,440,840 line is a nice suggestion as well. They're fantastic headphones, but you might find the bass a bit lacking if you're looking for a Beats-like experience. (I owned the 440 myself).