I personally use the Audio Technica M50. They are hands down the best headphones you can get for under $150. They are meant as professional studio monitors so they have a very neutral sound profile unlike the V-Moda ones that have been previously suggested which have a very colored profile with an emphasis on the bass range and thus have a more recessed, muddled mid and high range as well as poor sound staging. The ear pads of the V-Moda also get hot and uncomfortable much more quickly in case that is a factor for you. The V-Moda is comparable to Beats By Dre and are more suitable for bass heads and for people who care more about how stylish they look rather than the actual sound quality.
You can easily find the ATH M50 for under $100 if you do a bit of looking around, although I would be wary if they are priced too low as it is a very popular set of headphones and there are quite a few places selling fakes.
I would recommend buying the package below as the 3DS does not exactly drive quality headphones particularly well and would benefit from a portable headphone amplifier which would also allow you to color the sound profile a bit to suit your personal tastes.
http://www.amazon.com/dp/B00JZRXWRW/ref=twister_B00JZUO1CO
If you have a bit more cash to burn, you might want to consider the Newer ATH-M50x as they have a detachable cable and have updated ear pads that are noticeably more comfortable.
http://www.amazon.com/dp/B00JZRXWRW/ref=twister_B00JZUO1CO