Sennheiser hd 650 vs hd700

Does anyone have a strongly held view on whether the 700 is worth 2x the 650? I will be using computer source thru a rega dac and rega ear. I know it is not twice as good, but given my tendency to buy things 20 per cent different. My plan b if I don't get the 700 is to get the 650 and wait on a deal for beyerdynamic t1s. Thanks.
I have never really understood why people like the 650 or even HD800?

I have had the HD600, HD650, and the HD800. Both the 600 series are dark and dynamically challenged IHO. The HD800 is like putting a tweeter on your ear. No bass at all. Impressive for a moment but ultimately not worthy unless you EQ some bass in.

I think a pair of Beyerdynamic would see you getting much more music for half the cash. But to kill the headphone once and for all its time to get the Audeze. The finest by far in every area.
If you don't already have one I'd suggest you think about getting a good amp for the 650's as opposed to buying the 700 without one. Might be a far greater improvement than just getting new phones. I got a tubed amp for my 650's and am quite happy.
I have one of each - I've had the 650s for a couple years, and got the 700s a few months ago. I share Chadeffects' view that the 650s are a little dark, but I prefer that to overly bright headphones. I got the 700s because I had heard repeatedly that the 800s were very bright, and the 700s were a "toned down" variation. My personal view is that Sennheiser hit the sweet spot with the 700s. Very comfortable, beautifully balanced, transparent sound. Great imaging. In my view, definitely worth what they cost.

For those that care, I am running them off a Schiit Valhalla headphone amp connected to an Audio Research LS-27 preamp.
I find the hd700 unbalanced and not natural. The hd600 is still the sweetspot In the senn line. Very coherent, great mids, Speed AND body. The hd650 needs brutal power , otherwise its not as good as the hd600. The hd800 is bright and can't do the body as easy as the hd600 does. Get an lynx hilo or grace 903 with the hd600 and you will have a fantastic setup.
Save your cash...try the JVC HA RX 900 cans...very higher end Sennheiser sound (slightly muted highs) for way less...Im an AKG fan...but these are very impressive...regardless of price.....
I have owned the HD 600 which are one step below the updated HD650 and the HD800 I can tell you that the HD800 is one of the finest pieces of audio I have ever owned. An important note about these headphones, they are a difficult load to drive. Playing them through a less then stellar headphone amplifier may be a disappointment and definitely not a fair evaluation of these headphones. After doing extensive research, prior to purchasing the HD800's I purchased a Cayin Ha-1a Tube headphone amplifier and the experience is so awesome it is difficult to describe. I can tell you the sound is smooth as silk, nidrange is 5th row center,and the bass is rock solid rich and full not exaggerated. You will hear many albums for the first time! Pair the 650 or save your money and go with the 600's and invest in a good headphone amplifier
Well, Emster, there you have it. Six responses, and a clear consensus has emerged that headphone choices are highly subjective, dependent on associated equipment, and there's no accounting for taste. ;)

I think the moral to the story is that you are best advised to purchase from a dealer (online or otherwise)!that permits returns, and let your own ears be the judge.

Best of luck.