If you can find a pair to audition, I would suggest trying the Hifiman HE560 headphones. When I went on a quest for headphones for Hauptwerk, I auditioned headphones from AKG, Sennheiser, Grado, and Shure, but none of them had a tonal quality that I found pleasing for pipe organ, particularly in the bass department. I am a graduate of the recording engineering course from Fanshawe college in London Ontario, and have spent time in recording studios, and K701/K702 are regularly found in studio environments, but upon doing a side-by-side comparison of 702s against the HE560s, I was amazed by how much better the HE560s sounded (to my ears). Once properly "broken in", the HE560s sound excellent across the frequency range of the pipe organ -- deep, rich, natural bass, and not at all harsh in the upper registers. They are very light weight, and extremely comfortable to wear. They are not inexpensive by any means, but I believe they are well worth the price. Here is a link if you want more information:
http://hifiman.com/products/detail/167