I've heard the 9NT's don't live up to the rest of the range (and that the 1NT's are probably the best-sounding model of the lot). I can't confirm as I've only heard the 1NT's.
I can, however, confirm that the 1NT's require serious amplification. I auditioned them twice, at two different dealers. The first time was with my own system at the time - a Marantz CD6000 KI-Sig CD player and a NAD C370 amp. This was a very decent mid-level hifi, and the NAD at a conservatively rated 120wpc was not wanting for power. All the same, the system sounded good but not great - treble was sweet and detailed and lovely to listen to (the B&W tweeters are excellent) but bass was very lacking in control and precision.
The second time I heard them was at a different dealer with a *very* different league of electronics: Linn Ikemi CD player (£2000!) and a huge high-end American power amp (can't remember the brand or model) costing several thousand pounds. In this case the B&W's really came alive - they produced a gloriously detailed and realistic sound with fantastic bass (and the same sweet treble).
I have listened to Sonus Faber Concertinos (smallish standmounts at £600, + £300 for matching iron/walnut stands!) on serveral occasions, and I also find them to be excellent speakers. They sounded great when hooked up to more modest electronics (comparable to the first system I listened to the B&W's with), and I'm told they do justice to much higher-end kit.
I never had the chance to audition the two speakers side-by-side. I would have to say the B&W's sounded a lot more realistic and a lot more listenable - but only when paired up with very high end electronics (which isn't exactly a fair comparison...)
Cheers,
Dunc