I just got a used T1, gen 1. Wow. I'm sorry to say that my T90 (which I loved, until now) just sounds harsh and sibilant compared to the T1 gen 1. The T1 is a huge step up.
If you are really really into treble, the T90 might be a better choice. I'm into treble, sparkle if you will, and at first listen the T1 is just wonderful.
Computer -> DACCord -> Crack -> headphones