Making changes to the EQ can only be made when in the OSD menus and you can't hear the results until you exit. You can certainly make changes by ear if you have a recording engineer's experience with boosts, cuts, and Qs, but the vast majority of people would find it a very slow process.

I think the main use case for the Model 976's EQ is to use a room measurement and EQ modelling tool like Room EQ Wizard (REW) where the user measures the system with a calibrated microphone and the software recommends the EQ settings for a chosen target room response curve.

My personal experience going the REW route has been that I gained a lot of knowledge and experience about the acoustics of my room and the limits of EQ's abilities. I was really surprised to hear for myself (and validate with measurements) just how much improvement can be made with inches of speaker placement and aiming. Over time I added acoustic treatments to the point that I no longer engage the EQ.