Yep.. I've owned a grip of full sized phones.. HD600 (twice).. the entire HE-x00 (HE-500 twice).. LCD-2.. HD800.. a couple of the better "mid-fi" Beyers (880/600 & the T90).. even the Koss ESP-950 (which I loved.. and still regret returning.. but the 650 softened the blow of that dumb decision).. lots of buying and selling (check my feedback! LOL).. but I don't think I kept any of those phones for more than seven or eight months (HD800 included.. but I still do love that beast). I've had the HD650 for six plus months and while I plan to buy a planar this year.. there's literally nothing out there that would make me move the HD650 at this point... and I'm in NO rush to get that planar. As Jamie mentioned, the Crack's 'vintage' look makes for an excellent conversation piece and I've yet to have one (non-audiophile) person hear them and not be thoroughly blown away.
Obviously, headphones make the biggest difference in a rig.. but for me, the Crack made me appreciate and enjoy the HD650 more than ever.. the key word there is ENJOY. I forget about technical ability.. distortion specs.. driver speed.. etc etc.. The combo delivers to me something I and many others have desperately sought in this (expensive) hobby: contentment. I'm more content with the Crack/650 than I have been with any other phone/amp combo (I've owned) to date. I've heard better phones.. I've heard more capable amps.. but the HD650/Crack deliver a certain degree of sustained enjoyment I just haven't experienced (w/o spending significantly more to get).
Contentment is exactly what I'm after. I really think I'm also on the verge with the HD650 and if the Crack will help me achieve that then I'll probably go that route. I really love the way the crack looks and some of the ones I've seen look downright amazing. Plus it's not as expensive as some of the other amps I've been researching. The Woo amps look amazing as well but it's really hard to ignore all the positive comments the Crack/650 has around here.