Audyssey can correct for a flatter response, altho some don't prefer it. The graphic eq in the Denon cannot be used in conjunction with Audyssey, it is an either-or thing. Audyssey with the use of the external Audyssey app from D&M can give you some more flexibility (for example I have an older Denon 4520 without the app, and am pretty much stuck with the Audyssey curves as built into the avr). Graphic eq has the limitations of what center frequencies it is setup for, a variable parametric eq such as in a minidsp would be more versatile. You could possibly use a minidsp of sufficient processing ability on pre-outs of an avr, in between the avr and external amps. Most receivers no longer have a processor loop such as was often available with older 2ch analog gear. As I said, the primary purpose of REW is for measurement, the implementation of eq is not it's primary purpose and is limited in application thru particular gear.