The DT880's are less v-shaped and may not be as "fun," though if you want detail retrieval, they're quite impressive. Haven't heard the HD600/650 or AD900x but the Senns are supposed to be on the warmer side with not a lot of treble emphasis. Might end up being your cup of tea though if you're able to try it out. Keep in mind though that you'd likely need an amp as well with any of these.
I have tried out the T1. I like the sound. I see people describe the DT880 sound quite same like T1. Isn't true? I haven't try the DT880 yet. Hope I have a chance to try it out in M'sia. By the way, which amp do you recommended for the DT series?