I just unexpectedly got my AD900, just tried them with my pc setup and begun with some metal albums just to see if they're actually as good as the sr225 as many Headfiers believe.
The bass is perfect for my tastes, just as fast and responsive as the grados, with the same impact if not a tad more, the deep bass of a drum kick is there, but never gets annoying ( like it frequently is with the otherwise perfect dt-990pro or other bassy cans ). The mid-bass is fast and controlled, i can hear bass guitar even in recordings where it's quite drown in the mix, right now i'm listening to Iron Maiden' Seventh Son andi can hear Harris's bass lines way more clearly than all my other phones.
The mids are not as aggressive as the Grado, but surely as enjoyable, distorted guitars sound just right, less fatiguing but not too distant. Vocals are a bit more recessed than the sr225, and that's a plus for me, i don' t always like to feel the singer "shout" right in my ears. This is particularly evident on Death's The sound of Perseverance, where Chuck's voice easily gets fatiguing with the grados. The Dt-990 get this problem solving, but are still inadequate for fast metal as they tend to deliver muddy bass.
More atmospheric bands like Opeth sounds just perfect thanks to the added soundstage and instrument separation, even the early albums which are known to be very harsh sounding, and are nearly unlistenable with the 225.
Now i'll proceed to listen to some sample tracks of my main genre of interest which is progressive rock, let's see if they correct all the Grado's shortcomings even there
So far i am really satisfied with my purchase, sound and feature wise, as build quality and comfort is top notch.