My most abiding (and most used and enjoyed of all the cans I've owned) is my pair of Grado SR225. I've owned the K501 and HD580 concurrently as a complementary can to the SR225. I kept and further invested in the HD580 (HD600 grills and a Cardas replacement cable), and sold the K501 to a Head-Fier who wanted to use and enjoy them. I find the HD580 to be wonderfully complementary to the SR225, and the two together make a formidable set of listening instruments for all of my favorite music and movies. From my first listen of the K501, I always appreciated their quality, refinement and, relative to other headphone manufacturers, their value. I used the K501 as my main can for about six months, and then drifted away from it back to the SR225 and HD580. I've owned the SR225 for three years now, and I'm coming up on my 1 year anniversary on the HD580 - which are becoming ever more firmly ensconced in the easy-to-reach-for portion of my listening area - right next to the SR225.