I have tons of experience with NHT (been a 'fan' and owner of numerous models since the beginning). As far as powering these speakers, you should be more concerned about amperage than wattage. I had my 80 wpc Unico running them for a while and believe me, they put out all the clean spl's that you could ever want in a normal sized room. Having said that, I do concur that the NAD370 would be a better match as far as power requirements are concerned.
Also, the NHT's like their equipment more on the warm side... if not, your cat will be climbing the walls because of the unforgiving highs (I really loved most of my NHT's using a solid state amp and tube or hybrid pre amp to smooth them out a bit).
I had mine in a room that was 11.5 x 14 and they were just too much - the bass became too boomy and bloated in my room and no matter what, i couldn't do anything about it (I even tried stuffing the ports with medium density foam, which helped, but didn't cure the problem). This, apparently, was a common complaint about the 2.5 and 2.5i's. So, if your room is on the small side, consider yourself forewarned (The 2.5i's differ from every other NHT model in that they are ported - bad move on NHT's part)
Now, with respect to their performance for movie viewing - Excellent. Clear, articulate, dynamic and big-sounding. Really outstanding performance, in my opinion, for home theatre (and many, many visitors who have passed through my condo agree).
With respect to 2 channel audio, they are also very good (provided they have breathing room). They image like champs, focus very well and they really clearly delineate where musicians/ instruments are located in space). The NHT's upper drivers really have the ability to 'float' an image, given the proper material.
I'll put it this way: I sold mine and regret it. Now, I'm looking for a pair of the 1.5's (top part of 2.5i's) for my small-ish room (2nd system). I'm staying away from the 2.5i's only because they're too much speaker for the room in which they'll be placed.
hope this helps