NHT in Home Theater Setup

If you are going to use the standard 80HZ crossover points with a sub, I would go with the Classic 3's. If you don't want to use a sub, go with the 4's.
I use the 4's in front, the 3's as surrounds and the Classic 3 center. Using the 80hz THX crossover really negates any advantage the 4's have. Set up with the 4's crossed over at 40hz, the 3's at 60Hz and the center crossed at 90hz gives a much bigger sound overall. I'm also using an HSU VTF3 HO w/turbo sub. For movie tracks, you really need the sub. For music, I kinda like the 4's without the sub better unless it handles just the lowest of frequencies.
I driving the system with Parasound Halo amps all around.
I'm really a 2 channel guy and this is my first real go at HT. I'm still learning so you may get better answers elsewhere but this has been my experience.
BTW, the NHT's sure are good speakers for the money IMO.

I bought three of the M5 for the HT set up and I am very dissapointed as comparing to the Super Zero I owned some ten years ago. I have nothing but Bright and forwarding and super thin sound from these M5s...I can only use them for the movies with THX EQ on. Two channel listenning is Audio Hell. Despites all the good reviews, the M5 is not what you want if extended high is not your cup of tea.

I just purchased 4's with x2 x-over/dual a1's powering the 10in bass, 3's, ic4's, and a 3c. Still listening to the 4's alone in stereo/pure mode powered by Boston seperates(Sherwood clones). First let me tell you, with 4's you really don't need a sub. Placement flexibility would be my determining factor. Price wise...about the same for 3's with sub or 4's alone. Well, maybe a little more for the 3/sub combo based on sub money. I like the idea of knowing I have a main that can slam on its own w/o depending on any help. A sub to me is for movies. Old school I guess but most music does not reach down low where a sub best performs so the idea of using sub for music is a non-issue for me. Now don't get me wrong, watching a good movie and feeling the 'boom' is nice. That is what a sub is for. That's my take. The fours do what the threes do and more. Basically a three with a 10in woofer attached to it. And unless the 3's are on a shelf...floor space is about the same when you consider stands. Good luck.

I don't disagree w/ you about subs having a place of their own in any system, it is just in my case, and perhaps others, the 4's actually suffer from having a stand alone sub as opposed to bi-amping the 'subs' that are built in to the nht 4's. Using the two a1's (200/250/300w @ 8/6/4 ohms respectively ea. mono amp)to drive each 10in driver in the 4's will gives greater control, slam, and is completely adjustable by the x2 controls which has continuos adjustable phase, boundary compensation, and lfe level to tune rather than placing sub in 'ideal' spot. There is no doubt that a powered sub would be needed for the 3's to get the best of a&v. Besides, a 'good' sub would cost more than my mains and many people don't consider a really good sub costing more than the mains/monitors.