The DT770/80 is a solid choice if you like bass. They're piss easy to drive and sound good out of just about anything. Some complain about recessed midrange and highs, but I actually thought they sounded relatively balanced. I can even enjoy classical music on them (albeit not ideal)!
No experience with the HD595 or A900, but have had the HD555. Liked them at the time, but in retrospect, merely a stepping stone to the IMO much better sounding HD580/600/650. Based on the way the HD555 sounds, I wouldn't get the HD595, but I'm not basing this on any personal experience at all so feel free to completely disregard this. The sound is a bit too distant, recessed and not in your face enough for any real enjoyment.
The HD600 is a great headphone, but like SilverPilot already mentioned, the HD580 is better value. I have not compared the two directly, but based on separate experiences, the HD580 didn't sound too different (I did have HD600 grilles, HD650 cable on the HD580 though). I can imagine the HD600 being great for trance because it has pretty decent bass and nice treble for those eerie, metallic synthesised bits, but for rock, it might be too accurate sounding (similar to the K701). You might not get the most enjoyment out of the music even though you're hearing it the way it is supposed to sound.
Anyway, my two cents...