I did not have any luck finding a cable to test this theory with my HTC One and my Antelope Zodiac.
However, it turns out that FiiO is just getting in on the act with the new E18 device: an external DAC / headphone amp that plugs directly into the HTC One among other Droids, with its own supplied cable.
If UPS arrives today, will have more info soon, but imagine this will be a dramatic improvement and a must have for any self respecting audiophile with a Droid.