[Marximus]

FWIR, it sounds like the HD650s would fill the bill.  I really like the DT990s, but their treble can be a bit hot and sibilant at times.  I guess I'm not necessarily looking for something more laid back, but rather with a smoother, slightly less offensive top end.  I'm slightly concerned about a lack of clarity (read: muddiness) with the 650s, or for any other pair which might be in the same category of warm and laid back.  Is a uDAC-->E9 a sufficient setup for them?  I know that volume/power is not really an issue, since the setup drives the 600-Ohm DT990s fine.  I'd really like to avoid going further with amps/interconnects/etc.  The price of the 650s on eBay ($330ish) is absolutely my limit for cost, and I've tried/bought and sold A LOT of different headphones under that limit (I was thinking about it yesterday, and counted about 25), so feel free to ask if I've tried a certain pair.  Thanks.

 

[eucariote]

Haven't heard the HD650 so I won't be a great help.  But I find that my HD600 are the antidote to the excesses of my other main headphones, D7000 & RS-1.  They have deep, rich bass that is not fatiguing and never sneaks up on me like like a falling hammer, like D7000 sometimes do with electronica.  Similarly, they have very smooth and detailed highs that I can listen to without end and do not need to be tamed with tubes, unlike my RS-1.  Their mids are are also well-balanced and sweet, and are my favorite of among my headphones.  One note though- their near-perfect tonal balance does depend some on the amp.  Out my tube amp, their highs can sound a little soft so I tend to listen to them straight out the SS amp built into my dac, which sounds a little brighter, clearer and more spatially defined.  If I hadn't heard them out that amp I would have described them as a bit too fuzzy and warm.

 

[Marximus]

And indeed, I have tried the 600s.  Perhaps they're pretty close to "neutral," but I found them to be a bit lacking in warmth and bass impact, which is why I switched to the DT990s.  I'm thinking that it might have been better if I'd gone straight for the 650s, since they can be found for only like, $40 more online.

 

[jasonb]

Go for the 650's

 

[Satellite_6]

No real muddiness here.  

 

[Marximus]

Looks like you guys have pretty good amps, though.  You don't think mine will be insufficient?

 

[jasonb]

never used an E9, but i have no muddiness on my HD650's with my HeadRoom amp.

 

[maruzen]

hmm, the dt880 600 ohms will give you smoother treble, but you will really miss the low end if you compare the bass output to the hd650 and dt990. if you want the same clean signature with a better balanced sound, a bit of treble tilt compared to the hd650, smoother highs, with sacrifice in bass, you should audition the dt880 600 ohms. the midrange is a bit recessed with the dt880, pretty similar to the dt990

 

[Marximus]

Definitely not willing to sacrifice any bass.

 

[maruzen]

that complicates things
 
hd650 would be the safe bet. they do not sound muddy to my ears, only that the beyer sounds cleaner compared to the senn. but they have soft and less aggressive treble, with great bass response. maybe you need a good tube amp capable of driving them both well in the future. i am also on the lookout for such amp...