Well i agree about that T-90 is not that far from T1 , in fact in trying to be objective i would rate things like this :
T1 => 100 %
T-90 => 90/95 %
DT 880 => 80/85 %
Only listened the T-90 in a shop with some A/V receiver as amp .
But for the T1 /DT 880 it was at home using a A-GD NFB-17.2 as DAC and SPL Auditor for the AMP part .