When did we start comparing sources to transducers exactly? Especially Stax that have their own set of "characteristics".
They can sound fun, though I wouldn't invest too much if you're buying them for accuracy :|
Regardless, I'm pretty sure Carl has spoken of the difference transducers make (i.e. a lot).
I would agree that the reviews on Head-fi are based upon honest listening experiences, and most are without bias, placebo, or hidden agenda. As an example, here is a recent comparison of high-end headphones by a new Head-fier that to me is as pure as the driven snow. I see no evidence that there were any pre-conceived notions or conscious or subconscious bias present in it. It doesn't seem at all related to trying to justify the admittedly recent purchase. The reviewer is just trying to sort out the difference between the two headphones and share those perceived differences with the community as a whole.
Price alone can create pre-concieved notions that present bias. Nonetheless, very few would argue against transducers sounding different, they can measure all across the board with varying dips, peaks, and dispersion characteristics (and high levels of THD if we start heading towards super low-end, lower than Porta-Pro low). We could also include decay, though I'm of the opinion most decent quality headphones have it under control.
Arguably, in some ways true HiFi (reproductive accuracy) is easier to attain than the tuned sound some audiophiles would sell their first (and maybe the second) born for. Do you treat your gear as instruments or as tools is what it comes down to IMO.