The DTR9.1 adds 12V trigger outputs. Other than that, I think the only other differences are cosmetic. Warranty periods may also be different...
Displays: Sony VPL-HW40ES | 110" SI Motorized Slate screen | Pioneer PRO-150FD
Sources: Sony BDP-S5000ES | Dune HD Smart D1 | Roku HD | LG LST-3410A HD-DVR
Speakers: Nearfield Pipedreams 18 (L,R,Sub1,Sub2), Pipedreams 15 (C)
| Magnepan MC-1 (WL, WR, SL, SR, SBL, SBR)
Audio: Denon AVR-4311CI | Bryston 6B-SST | Bryston 14B-SST
Control: Control4 home automation