need more smoothness

Linn gear is smooth??? Give me a break. Talk about bright and painful, IMHO. So sure, blame it on B&W.
Cellorover, B&W tweeter's resonance is more like 25kHz, not 20. Monitor Audio IS around 19-20kHz.
Treat the room, aim the speakers more straight ahead than at the listener, and try smoother electronics whether tube or low distortion like Musical Fidelity.

Cdc-- I may not have communicated enough details. All metal dome tweeters resonate. It is inherent in their physical properties. The research found resonating frequecnies at 20kHz. This does not mean that this is the only point of resonance. Most start at 20 but really begin to ring at the 23-26 range. So, the B&W is right in the middle.

I will see if I can get a copy of the preliminary findings and methodologies and post it.

Cellorover, February 2004 Stereophile says the B&W 705 has a PRE-resonant notch at 25 kHz and resonant frequency is "just above 30kHz". Not bad for a metal dome tweeter.

i'd blame your speaker cable and mostly, your NAD cd player...

when i doubled up on CV-6 speaker cable my highs went from being forward-in-your-face to quite laid back and smooth. other big improvements in taming the nautilus tweaters were good power conditioning (incl. a good home-brew power cord from a hosp. grade outlet) and interconnects (i like AQ's coral line, for CDM1s you don't need anything more than good copper aka silver seemed too bright).

I agree with the poster who suggested that your problem is with your source. The 1nt is very sensitive to partnering components. Any tonal brightness in your system and the 1nts will pass it along to you. As well, the rotel amp is not the last word in warmth or refinement,very capable though it is. My suggestion would be to borrow a couple of different cd players to switch between in your system. I think you will find that the 1nt will convey the sonic differences between those players in a way that will be quite clear.As well, I would suggest that the Rotel-though very good, may not have the kind of current or stability that will bring out the best in this speaker. This is a very good speaker, by the way. It may not be your cup of tea, but given the right system the 1nts are capable of truly impressive sonics. I think you are on the right track to question your electronics