While in Hong Kong the past week I demoed Audioquest's DragonFlys with my H6s and I was actually extremely impressed... surprisingly so. Very powerful and quiet amps.
To my ears there wasn't a huge difference between the Red and Black using my H6s. I ended up buying the Black with the Jitterbug and not the Red model as I preferred the Black DragonFly's slightly darker/softer (more mellow?) sound signature and lower volume control... it was much easier to fine tune and adjust to a lower volume than on the Red which was much, much louder due to its higher amp output. So I saved myself some money choosing the black variant over the red one as I hadn't quite realized there was a dramatic price difference between the two!
I listened to another Audeze Deckard (my H6s sounded as great as they did on another one a few weeks back) and when comparing with the DragonFlys I honestly couldn't pinpoint any major improvement with the Deckard so I am definitely pleased with that revelation. I guess my H6s just needed a little bit more juice to deepen (tighten up) the bass and expand/broaden the sound stage and timbre... anything beyond the DragonFly Black level is simply overkill. All in all I now have a perfect home and portable headphone dac/amp solution!