Started with Soundmagic HP150 - First impression was that it was way too much a basshead can, but then it turned me into something of a basshead.
Q701 - had these at the same time I had the HP150, and they were just too bass light for my tastes (did not try the bass mod), so they went back.
HD600 - I simply love the sound sig of the Sennheiser, but it would not go down low like the HP150.
Shure 1540 - too much bass, so by this time I am getting real confused.
Fidelio X-1 - Huge bass, not too bright, but the bass doesn't sound exactly clean to my ears.
HE400i - problem with these was my preconceived notion after reading the thread on them, that they were simply going to blow my away. I liked the mids, but again, they would not reach as low as the HP150.
HD650 - as close to "perfect"as I have gotten. I don't care for too much treble, and I love the midrange on these, bass sounds very nice to me, but it will not go way down low.
Now I am beginning to come around where I'm not so much of a basshead, it's just that there are certain songs that really test how low a 'phone can go, and it bugs me when a headphone can't deliver there. These are rare, so I can give that up, but I know it's there.
My "test" tracks are Ry Cooder's "Drive Like I've Never Been Hurt" off his I, Flathead CD, and Dire Straits, "Iron Hand" on their On Every Street CD.
I can hear the lows on these tracks on the HD650, it's not like they are not there, but listening to these tracks with the HP150, or the X-1, the deep lows are in a whole different league from the HD650.
To my ears, the HD650 do everything better than the X-1, except those deep down lows, which is why I say they are as close to "perfect" to my ears as I have heard.
I know when I return the X-1 I will become accustomed to the HD650. Furthermore, if I had never heard my test tracks with anything other than the HD650 I would be perfectly satisfied.