I have had the same experience. There was some video review that compared the NH and the Z1R. The reviewer said the Z1R had better bass than the NH. I say to myself "no way!".
It is better. The Z1R is on another level but much more expensive so it should be. I liked the Nighthawk a lot when I had it but I couldn't justify keeping it after getting the Z1R.
I think the video about the comparison was made by phototristan and he goes by Mediahound on head fi. Not Z.