An iPhone drives the 75's with +47 ohms just fine. No AV, stereo receiver or even portable amp is necessary.
I'm not going to bother DBT over $50. Sorry if this is not credible enough. The headband, resin coated housings and pads make the majority of the difference. Impedance gives different flavors, its not a necessity but the deep bass does sound better to my ears, real or imagined, that's all that matters but with sweeps and tones I've heard 40hz at decent volume compared to 60 and above. I'm also sure there is variance in a product so cheap.
Here is an easy way to add custom amounts of impedance: http://item.mobileweb.ebay.com/viewitem?itemId=290372905689
I didn't suggest double blind test, only that an ordinary blind test would be useful and credible. In a case like this a blind test is as easy as the subject closing their eyes while their friend places the headphones on their ears and notes their impressions on playback. I'm not trying to put anyone on the defensive or tarnish their pleasure and am happy to start with the assumption of goodwill in and by all parties. I'm not one of those people who assumes malice or dishonesty and/or tries to berate people into silence by having a bunch of people arrive and shout insults while claiming the uniform nature of rent-a-mouth nastiness to be evidence of objectivity
It would actually be interesting if someone could do such a direct comparison, especially one that doesn't rely on trying to remember what the unmodded phones sounded like a few weeks ago as this is intrinsically too flawed to be meaningful.
I have the headband and found the sound difference is actually about position, not clamping force (a bit of bending and the clips can have the same clamping force as the headband).
My understanding is that iPhone output impedance is below 5 ohm so the impedance mod is probably superfluous. The iPhone would drive the KSC75 equally well before modding as after.