apparently they do work out of the box, just not as good as you expect.
most headphones are around 38Ω and phone will fully drive the headphones the manufacturer intended to.
you're literally only using 70-80% of the $1500 you spent with your phone. to get full performance you NEED a powered jack.
i just don't get why you would want to spent that much for something you can't use all the way.
You have absolutely no idea how impedance works. Where did you get that 70-80% figure from, your ass?
Headphone amplifiers (or "powered jacks" as you keep referring to them) cannot make a headphone sound better. A hard to drive headphone is like a heavy weight: it can put more strain on the amplifier and degrade it's performance. However, the amount of performance degredation that can occur at this point in the audio chain is absolutely miniscule. Most of the time what happens is that it clips at extreme volume levels, but you shouldn't be listening that loud to begin with so that's not a problem.
The DAC (digital to brown townog converter) is a lot more important, and is most of the reason why the headphone gains performance out of better gear. However, most phones have very good DACs nowadays because good ones are becoming cheaper as the technology matures. The HD800 is a headphone that is very transparent to the source material, which is why the amplifier isn't quite so important relative to the DAC.
And back to the original argument: yeah, most consumers will never be able to notice something like this or even come close to appreciating the full quality of these headphones, but that still doesn't make Sennheiser's price hiking acceptable.