Go into the 975 and 976 forums and see that everyone praises the 975 for its sound quality over the 990 and most say the 976 is as good or better than the 975. I would expect the 976 to outperform the 990 but I love my 990 for music. As far as room correction goes, the 976 doesn't have an automatic version but it does have a parametric equalizer which allows you to use room EQ software to adjust your room any way you like.
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Music system
Model 990/7500/Magnepan 1.6 QRs/Technics SL1200 MK2/Aperion S-12 Subwoofer/OWA3/Sony NS75H DVD
APC H15 Power Conditioner

TV System
Large Advent Loudspeakers/ Polk center/Monoprice surrounds/Panasonic Viera 42 inch/Onkyo HT-RC260/Sony BDP S590/Directv


Home Theater System
Onkyo PR-SC886/Outlaw 7125 Klipsch RF-82 L/R,RC-62 center, RB-35 SR/SL, BENQ HT1075, Outlaw LFM1-EX/OPPO BDP-83/Directv
Harmony ONE
Blue Jeans and Monoprice interconnects
APC H15 Power Conditioner