The change to 2.5 way should fix some of the issues I had with the 5th Gen C150, the narrow beam. Hopefully a change to the crossover should fix the really harsh midrange, a 2.5 way should be more like a 3 way even though it's asking a large driver to reproduce the main vocal range.
Actually I have heard the 6th gen C150, I bought a subwoofer from someone who had one, so I heard a quick demo from them to prove the sub worked ok. The center sounded fine in a quick non-critical listen in someone else's house, yeah so probably fairly worthless.
I think (hope) they just made some poor decisions on the 5th gen and the update has fixed everything. Many other manufacturers manage to produce a similar center without those issues.
Looks like MA probably didn't sell too many C350's as they have shrunk it into the new C250, glad I got my C350 when I did, still extremely happy with it.