John, I've discovered some very interesting things in my listening sessions with the M3, M5, M100, 1000-3 and 1000-5.
First, when watching movies, the mains don't matter. Surprise! I can't hear a difference between any of the above models in 5.1.
Second, when watching movies, the external amps don't matter. Surprise! My Onk is more than good enough for my 4,200 cu. ft. room and 13 foot MLP.
Third, for 2.1, the speakers matter a lot - a lot more than external amps. As I've said umpteen times, the soundstage and imaging are very similar between these three models and that's where it ends. The M5 is worth every penny over the M3. It is more than twice as good. No one I know wants the M3 when they hear the M5. The difference between the M3 and M100 is very stark. Not so between the M5 and M100 but when one listens closely, one hears things they can't unhear. The hand claps in Unsquare Dance sound like hand claps on the M100. On the M5, you know they are hand claps but they sound less human. You'd never know they can sound better than the M5 until you've heard the M100! My buddy (and Ian knows this) listened to my M5s numerous times and was very moved with the sound. But when he heard the M100s, when he heard those hand-claps, he wanted to buy them off of me. Then his wife stepped in and we all know how that ends.
Fourth, if you want the realistic sound of M100s, you better have a big room or they will boom like the dickens. You can plug the ports, apply XT32 and they'll still boom. Besides, plugging the ports changes their character. This is why I find the M5s to be the sweet spot. They work in big or small rooms and they sound excellent enough.
Fifth, for 2.1, external amps can matter. If you are planning on running the gain around 0, even the M3 sounds better with a 1000 but I wouldn't recommend running an M3 that loud because it's at the limits. If you're running M5s, the 1000 may not be enough for some songs unless you're sitting 8 feet away. And if you're running the M5s that loud in 2.0, you will hear distortion because a single HP driver can only go so far. If you're running M100s, the 1000 can be very good and anything more is for longer listening distances than mine or for very short periods of listening otherwise you will go deaf. Even the 1000 though has its limits and I can shut it down before the Onk pre-amp, M5 or M100 give up. That's where the 1500 comes in and can take the M100 right up to its compression limit.
Sixth, even in a largish space like mine, with M100s, I can live with my Onk with no regrets. Not so with M3s or M5s because in 2.1, they don't have the 'nads for some very dynamic material.
