anyway, recentely i purchased a HD650 abd IMHO they are very neutral sounding headphones... I dont think their bass is too much, and it is not bloated or muddy in any way, it is super tight and the treble extention is right on the spot IMO. If you want coloured, get the denon AHD5000 (or any of that series) or grado for super bright (and super awsome) sound.
the hd650 just need some burn in time and and good amplification.
I also didn't like them in the first 10 hours, but after some burn in (and my ears got used to the new sound) I realised what i am dealing with...a very high grade audiophile can indeed.
for me the hd650 are a combination of neutral and fun altogether.
but again...they sure need some very good amplification and source. my headroom ultra micro stack is handling them with enough authority, but I just feel that I can get much more than that. my next step will be to go balanced ... there isn't better than that.