I can't compare the 1911 to the 667, but I did demo the well regarded Yamaha RXV 3900, and a Yamaha 565.
The lower end Yamaha just didn't control the bass at all well. The 3900 did, but the bass was softer and without the same attack, and at 3 times the price of the Denon it didn't give enough in terms of extra detail to warrant the extra expense, at least with the speakers I demod with, (KEF 6005). The Yamaha had a nice natural sound, but a bit too laid back for me.
But in terms of the 1911 I've found it a nice amp, good detail, good bass control and texture, and good with music. The Pioneer 920 when I demod it again just didn't have the bass control or snap, though it seemed to decent and detailed higher frequencies.
But others often see it in different ways. To me a lot of it is down to the type of sound you like, and for me the Denon had no issues as such whereas the others did, but I like the Marantz / Denon type sound.