Very nice review!
I definitely agree with you on a lot of the sound quality points. The PRO 900 is probably amongst the worst of headphones I've tried in terms of fidelity and the price you pay for it.
I can see why you would recommend them with a warm-sounding amp. I tried them through a FiiO E7 and they were crazy bright to my ears. Sure the bass extension and impact was good, but the highs were so bright and annoying that I didn't listen to them for more than 5 minutes. The midrange was also really poorly presented and the upper-midrange (female vocal's ssss sounds) were sibilant. Personally I wouldn't pay more than $250 for them. Evidently, others really like this headphone.

Thanks!
Yeah my opinion exactly.
I dont know why they are so popular.
Sure there is a charm in their sound...
Too bad the highs and sibilance will kill you before you realize it.

try the beyerdynamic dt 990 pro! ...gonna kick some serious A*** and only half the cost of these

Might try the Beyers in time, But for now, Im decided my next purchase is either the HE-500 or HE-5LE
Still, thank you for your advice.
Best regards, Luke

its not just about the can per se i soon discovered, system n cable match up could make or destroy a "can". Then there are the pads...the small mods... i am lucky i managed to tame this beast thru a tube amp, jmoneypad and some nondescript cables.. Just trial n error, i dunno rocketscience...all the best to your next TOY!!!!

Now, I am not saying this is not possible, but why should I the customer go through all these hassles and extra buyings to make this headphone "listenable"?
It isnt orthodynamic... You dont expect the need to invest further into it.
This review was as is, with a few aftermarket, albeit cheaper cables.
Yet the headphone simply does not perform well. At least to my tastes
Best regards, Luke

HE-6 review coming soon

Do these distort at high volumes?