I've got a Silver Dragon V3 I'll be parting with soon, it is definitely better than the blue.
At the price you quoted me, it is a steal. But you need to have a XLR balanced output to use it (which I think is the best output format for listening to the HD6xxx).
Thanks for the detailed write up. That's very similar to what I thought comparing the Cardas cable and the stock. In the overall scheme of things (i.e. compared to switching out headphones), it's relatively subtle and I can understand why some may not hear a difference and/or don't want to spend the money. But it makes a difference for me too and this is a hobby so I play.
It's funny, I also though my HD650 sounded more dynamic because there was a noticeable volume difference. For me, it probably is the pads since the (original) ones on my six year old HD650 are flaccid and the ones on my HD6XX are firm. I actually like the sound of my HD6XX better than my HD650 once I adjusted for volume.
My kid liked the "fresh" HD6xxx better than the HD650 - he thought it was more crisp on the top end. But he agreed it was rather flat in comparison.
Agree on the diminishing merits of upgrading cable at a certain point. I also have a Cardas Clear cable for my LCD3's, and while it was a "clear" improvement over the stock Audeze cable, the difference was not as dramatic as the upgrade from Sennheiser stock cable.
However, purchased smartly, a basic cable upgrade can really elevate the performance of the HD6xxx.
On the unrelated topic of power - while the HD650 doesn't need a ton of power to work well, using a significantly more powerful amp seems to really changes the character of this headphone. I remember when I switched from a portable amp to the Woo WA22 and later to the WA5 , the difference on the HD650 was pretty massive - more so than on the LCD3. Looking at the power output on both amps (see http://www.wooaudio.com/docs/wooaudio_amplifier_comparisons.pdf), you can identify what is happening with the more powerful amps.
You wouldn't initially guess that from the Hd650's good specs - 300 ohms and 103db sensitivity, which means that it can play reasonably loud without needing tons of power. But as this article (http://nwavguy.blogspot.com/2011/09/more-power.html) describes, many tracks played at higher volumes push the HD650 to demand significantly higher voltage, in some cases way beyond what portable devices can deliver.Most users here, however, are likely to pair this headphone with a much lower powered amp, probably even something battery powered. It will still sound generally good, but the lower power amps on these devices aren't really capable of demonstrating the full potential of the HD650.
Higher powered desktop amps like the WA22 can push 1100mW at the HD6xxx's impedance, but the brutally powerful WA5 is capable of delivering 6000mWs into the HD650! By comparison, a popular entry level amp, the Schiit Vali 2, can push just 270mW max power at 300 ohms - more than plenty to power the HD but nowhere near what the more powerful Woo delivers. It's not until you get into Schiit's top end Ragnarok that you see similar power levels (1.7mW).
For my ears, the additional power translates into better driver control and significantly better dynamics with much lower distortion, especially at higher volumes. On a higher powered amp, the HD650 changes from a really good sounding, if polite, headphone, into something way more dynamic. Bass has much more energy and impact, and that famous dark veil seems to disappear, so much so that I wonder if the real issue with the HD650 is about the user's amp choice, not the inherent limitations of the HD650.
If you are looking seriously at options to improve the HD6xxx's dynamics and performance, you should first spend your money on a more powerful amp whose output specs are better matched for the HD650's higher impedance and lower . Until you do so, cable upgrades will deliver improvement but you won't be able to hear as much difference as when the HD6xxx is powered appropriately.
