I use the DR3 for my left right and center... I suppose DR2 for just LR and DR3 for LCR would depend on the speaker and layout you used.
7.3.4 setup: Emotiva RMC-1, XPA-DR3, 2-XPA-4, feeding Revel Performa3 bed and C763L ceiling speakers Mini DSP for bassEQ feeding Dual JTR Captivator 4000ULF (6k amps) and Clark Synthesis 429 shakers with OSD power Display: JVC 25th NZ9 projector with 135" 16x9 Stewart Cima Neve screen in a cave!!! Media: Nvidia Shield with Plex, Channels DVR and various streaming services