The headphones I'm using are Audio-Technica ATH-M50s, quite well regarded. I bought them for about £135 two years or so ago. Don't get me wrong, like you say the bass ouput is not to be sniffed at. However, there's still no getting around the sub bass presence that a larger speaker can deliver. I'd also argue that the detail my studio monitors output was above what my headphones could deliver. But they were £350 more expensive so you'd expect that I guess; I'd relish being able to listen on some Audeze LCD-3 headphones for comparison. Like I said, a combination is best. Headphones pick up things monitors might not, and vice versa. However, ultimately I'd choose speakers because I find it a more natural listening experience. Saying that, I'm not sure much can top long train journeys through beautiful landscapes with a good pair of headphones.