I think you're confusing two very different points in the history of the Universe. The CMBR was emitted after the decoupling of matter and radiation, as you mentioned, but this event was over 300,000 years after the Big Bang. And you are correct that there could, in principle, be observable signals emitted before this event in the form of neutrinos or gravitational waves. The observable universe, however, is defined not by reference to the signals emitted at the decoupling event, but rather the start of the inflationary epoch, which was merely
10^-36 seconds after the Big Bang. So, the OU is big enough that it encompasses all of the space from which any signal, even neutrino or gravitational, that might have been emitted 13.75 billion years earlier that could eventually reach us.
But, terminology aside, this still leaves your question: How much farther could we see if we could pick up neutrinos or gravity waves? Not a whole lot, unfortunately. Most of the expansion of the early Universe occurred during the (aptly named) inflationary epoch, and that lasted less than a tiny fraction of a second, leaving very little time for a neutrino or gravitational wave to travel before the Universe became very large. The expansion that occured in the following 300,000 years is negligible by comparison to that first tiny moment, so you won't get a whole lot more than 300,000 light years out of those neutrinos. I'm too tired and lazy to do the math to find the radius of the surface of last scattering, so I'll run a quick Google search, and...
The final answer is that the visible universe, or that which is not obscured by the opaque matter that dominated in the first 300K years, is a sphere with radius of 45.35 billion light years, while the observable universe, which is everything that can observed in principle, is just a bit further at a radius of 46.5 billion light years. So, yeah, we've got most of it covered.