I listened through the whole Audio-Technica medium-highend open and closed line (That is AD700, AD900, AD1000, AD2000, A2000X, A900x), to some Beyerdynamic open cans (the 990pro was absolutely filthy with yellow brownish cushions; I put it on anyway), to some AKG cans (they didn't have the K70x out though, so I asked for the k550).
To my regret the Fiio really didn't really have enough power for the Beyerdynamic or the AKG (which were seriously lacking bass).
I got the AD700 for my Girlfriend some time ago and quite enjoyed the sound so I'm planning to get some open cans for myself. Now I am still quite new to all this but the AD2000 just owned every single other can I listened to (didn't dare to ask for a sennheiser HD800). Just as described in older reviews, the sound is nearer, it has a much improved bass over the lesser Audio Technica and the music just sounds great (I mainly used 24/96 Jazz (hardbop) and classical (chamber music/solo piano) files today). One thing that bothered me with all the open cans from Audio Technica was the percieved build quality. Apart from the AD2000, which uses metal framing, the lower open cans plastic just felt cheap. Sennheiser felt like crap. The AKG cans had the best materials I think, even better than the AD2000. But as I took a look around at some lower-end Sony headphones for about 80 dollar, it seemed they were almost as refined as the AKGs and had a much improved material selection over AD700-1000. Now the AD2000 are about 47.000 Yen when I buy them over the internet. Right now this equals around 600 Dollar. I was initially planning to go for the AD900 since they are comparatively cheap (17.000 Yen=220 dollar) and I didn't want to go highend right away but looking at the materials just makes me feel outright stupid spending that amount on a domestic brand which should be cheaper than in the US or Europe. Also considering the ridiculously weak Euro at the moment it just seems to make more sense to go for something else with better materials. Obviously I want something thats not as hard to drive as the AKG K7x or the Beyerdynamic so the AD series just seeed right. I also quite alot enjoy the airy presentation of the AD-series (thou the 2000 is alot more direct than the other ones). I don't really like the sticky sweatyness of almost anything else but velour cushions so thats another thing for me to consider. I would like to try out the hifiman headphones but in Japan no avail. I'm quite happy with my Sony XBA-3 IEMs and in disregard of what other people say I believe newer technology really makes a difference so maybe I should consider HE-400? Or the HE-500?
Any advice would be appreciated since the only two options would be to spend money on either the AD900 or the AD2000. But for 600 dollars I could almost get the HE-500 or the HE-400 with a better amp.