HBB, I own the D600 and not only is it a basshead certified beast (I listen to them out of vintage amps - epic with the loudness switch thrown) but they are also very good across the board.
So that said, when comparing some graphs last night, the D7100 has a fair amount MORE bass than the D600. Did you test them? Check this out.................
*disclaimer - I'm NO graph reader/believer/etc but for pure bass response I've found these to be useful in finding the sweet spot.
Bass charts tell me how much a driver has been pre tuned after I have listened to it. I never see charts unless something seems amiss (never seen the one you showed till you showed it) Off and e12 with my 2 tracks and the Beats track the 600 shined and they are not advertised as such. Seemed odd so I tried it v.s. the Raver and 7100 and for some reason it was still shining. I figured it would raise eyebrows since it's not the basshead set and not the expensive set....had not seen a chart though. (I have extreme bass slopes at 35-45Hz bump and 60-75-80 mountain)