tama, I like your formulation of "Monism, dualism, holy Trinity and Infinite forms of infinities". I'd even add Empedocles' four elements to stretch it out a bit before departing for infinity. However one "number" is significantly missing from that ordered set. It is of course zero - the origin, the point at which all numbering collapses. This may be what the term "non-dual" points to, rather than the notion of one.
I guess this is what people mean when they speak of the void (or more pretentiously, The Void) - the moment in which all conception ceases, along with all numbering, motion and relationship. What I'm still wrestling with is my all-too-human tendency to conceive of the void/origin/zero point as Unity. It's a seductive notion, that the void can be approached through unity. I suspect, however, that they are utterly different "things", and that the void is as inaccessible from unity as it is from duality (trinity/quaternity/countable infinity)
Going back to Empedocles, he has an interesting notion (according to Peter Kingsley, at any rate) that the unity of which we are all so desperately fond is a pure deception - a mirage, a veil drawn before our eyes by Aphrodite as she mixes and incarnates the four divine primordial elements to create this illusion of reality.
Of course, even the Advaitin sense of no-self remains only a conception unless one is residing within it. Being human means moving in and out of the not-two state of complete "awareness-directed awareness", and even most awakened ones seem to spend a lot more time out of that state than in it. When one is in it nothing can be conceived. When one is not in it, conception is all there is.
Is it helpful to talk about this? To the extent that it helps us remember who we are, perhaps. Beyond that, no. Typing about it on the internet is an interesting, if somewhat eccentric, pastime. I enjoy typing about it, but that's only because I'm not in it. In those evanescent moments when I have been graced by it, "I" am nowhere to be found - neither on the internet, nor in my living-room.