Need help choosing open headphones in the $200-$300 range

[zazex]

I've never heard that from anyone else. I understand that you're reporting your experience, but these sorts of rumors surface all the time about other models (and occasionally they would seem to be true, such as HD800). I would want to hear it from large numbers of people before beginning to consider it.

 
 

  I mean that for me the HD650 has a slightly more liquid, smooth sound (the HD600 is very clear sounding, I'm just nitpicking)..

 
 

   
Other members have mentioned this before and it was obvious to me while comparing my HD650 and HD600 so it might be worth considering (otherwise I would have kept the HD600)...  

 
 

the difference between HD650 and 600 are minimal compared to other models, you can't go wrong with either model. Technically HD650 is slightly more refined and have better driver matching. (from objective data, not from personal impression)

 
This discussion brought to mind Tyll's article in Inner Fidelity
from about a year ago.
 
It's four pages; I'll quote just a two paragraphs here (hope doing so is OK):
 
 
The sound of the HD 600 is overall smooth and slightly warm sounding. Like most cans of its era, the sub-bass response is a bit weak and somewhat loose, yielding a mild mid-bass bloom to the sound. The transition from mid-bass to treble is very even and well balanced, though the top treble octave might be just a tad shy of neutral. I really think the "Sennheiser Veil" myth with these cans is mostly the result of being compared to the many overly-bright headphones in this category (Grado, Audio Technica, AKG).
The HD 650 is rather more problematic to me. While the sound remains very similar to the HD 600 and does seem a tad more refined, it also seems a bit warmer, lusher, and thicker...more "veiled" if you like. Yes, in this case it does seem to warrant the discriptor. Just a bit too much of good thing. I still think it's a great headphone and have no problem recommending it, but with a $100 lower price, and a more neutral and snappier sound, I think the HD 600 is the better buy.
 
http://www.innerfidelity.com/content/very-important-sennheiser-hd-580-hd-600-and-hd-650 (at page 3)