I would think that the tweeters in the NHTs are much better than what's in the Polks. I listened to the step up RTi series and was not impressed. I am impressed with my Zero 2.0s ( for the money and size).
The NHTs are sealed and smaller making placement easier. I use 5 in a 13x14x9 room on 40watts/channel and for movies they rock pretty good. I do need more power for music though.
Klipsch RF-62II, RC-500, RS-400, SVS PC12+,
Def Tech SC8000
Harman Kardon AVR 1600
PS3, Apple TV, Sharp 70" Qattron