Last Saturday, I had this problem and ended up testing loads of different headphones at three different stores in order to find something suitable. There are many different headphones situated in the $300 sweet spot, making choosing the right one a touch choice.
1. Bowers & Wilkins P5: The P5 from B&W are almost perfect for their intended use: listening on the go. They fold flat, which is nice when compared to others. I've found the sound of these headphones to be quite good, but you'll pay a bit extra for the brand name. Nevertheless, if you want sturdy headphones that have a minimal design and aren't too loud, then these headphones should fit the bill. I was able to find these for $240 new.
2. V-Moda Crossfade LP: These headphones are often overlooked, but the sound quality was very good, especially considering you can find these for $120-150 at various online retailers. The look isn't for everyone, but ultimately, for some people, the sound is more important than how they look. There are some variations of colors and finish of these cans.
3. Audio Technica ATH-ESW9A: These headphones have a wooden housing made from African Padauk, and they come with 42mm neodymium drivers that sounded very good to my ears. They also fold for storage, which is perfect when you're on the go. You can find these headphones for $200-250.
4. Beyerdynamic T50 P: The T 50s come with Tesla technology and are good on the go, since they have an external noise shield to dampen sounds. While not as sexy as some of the other headphones, they definitely sound good, and since you can find these for $200-250, they are a good deal.
5. Beats Solo HD: I have the Beats Studio, but I find them too large to use every day when I'm about town. The more diminutive Solo HD are perfect for this. However, just like all Beats headphones, they are a bit overpriced for what you get. The bass response is very nice though, and if you can get a pair for $120-150 they are a good buy. At this price, you'll probably not have the pick of colors you'd like, but the sound is the same. MORE HEADPHONES ON APARTMENT THERAPY: • 5 Thin & Light Headphones • Top 10 Headphones • Audiophile Headphones: When Hifi Speakers Are Impossible • Bowers & Wilkins P3 (Images: Flickr member Noelas licensed for use under Creative Commons, Flickr member FortyTwenty licensed for use under Creative Commons, Joelle, Jason, Range Govindan, all others as credited above)