Pink Floyd and Weed

I have Sen 650's....they are very much like the 600's.   I can tell you the highs and lows are truncated, but the mids are very nice.

stringreen, thanks! I did not consider a different set of phones, I tried a friends set of Cardas in-ear phones and there was more bass but they did not have near the clarity of my HD600's.

So, what this tells me is exactly what you observed, at the extremes, (mostly the bass) the HD600's truncate. I really like the sound of them, but am left wondering if there is a more full range option that can still hold on to that clarity/airiness that the Sennheiser's  possess while producing that wanted bass? I am concerned it may be cost prohibitive to best the HD600's. Thanks again!  

@grm -- I bought a Quicksilver Audio headphone amp a few months ago. I have the Senn HDXX (same as 650 and somewhat similar to your 600), Focal Clear and Hifiman Arya. The QS amp was a night and day difference. If you read my other threads, bass is one area where I saw the most noticeable improvement. It is an amazing amp!!!

As for your 600s, all I can say is that although my other two headphones are much more expensive than my HDXX, the Senn punches way above its price point, and definitely scales with better amplification. Try it with the Quicksilver amp, I think you will be pleasantly surprised what the 600s are capable of.

arafiq, thank you! I looked at the QS on-line and it is one impressive looking amp. I need to research where to obtain one where I can "buy and try", just in case it does not work out for me. Is there any low level buzz from the tubes? Also, I noticed it does not have audio pass-through, I kind of need the pass-through because my main amp does not have a pre-amp output or tape loop, so I am using the pass-through of my MF amp to connect to my PC speakers. Based on your feedback, as well as from others, I'll hold on to my HD600's for now. 

I really appreciate your help and suggestion!

grm.....I just got Grado GR10E phones.  They are in ear, yet if teamed with a really good amp, are faster, cleaner, more solid low end, etc. than my 650's