The 990 has a couple of more inputs plus the auto setup routine. If you want the best sound quatity possible from an Outlaw product, get the 990. If you need a phono input, get the 990. If you are going to do alot of stereo listening get the 990.
The 970 is an excellent product also. I would say the if you budget is tight and none of the above apply get the 970. If you are primarily going to do TV/Movie watching get the 970. I would say that the 970 compares favorably with Rotel & B&K where the 990 comparres more with the Anthem/Arcam family of processors in terms of sound quality.
I own a 970.
This has been covered extensively, but the above is my synopsis.
Regards,
Charlie
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Charlie,
Outlaw 970, B&K AV5000, Paradigm Ref 20 and CC (V1), Martin Logan Dynamo, Sony 42" RPTV, Toshiba HD-A1