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.