You still need a sub with the M80s. Even if you are going to listen to just music (unless you listen to only flutes
).
You don't have to use a centre for 5.1. If you do use a centre however, it anchors the dialogue and it sounds like it's coming from the centre over a wide listening area. You lose this benefit with a phantom centre. Dialogue and bass sound very different with a phantom compared to a dedicated centre speaker. But the centre does have a major drawback. Many listeners don't know how to calibrate it properly and they end up making it too loud thereby negating some interesting effects that the sound engineer built into the track. You can't make this mistake with a phantom. People also make the same mistake on surrounds but that's not nearly so disastrous (at least that's what my ears tell me).
I am starting to really enjoy listening to CDs in Neo and PLIIx. For some recordings I enable the centre and for others I disable it for a phantom presentation. For movies, I always enable the centre.
You'll have a lot of fun playing with your system I'm sure to establish what's optimum for your environment and ears.
