The N-26II are basically the same, they are just made of wood rather than plastic but the acoustic qualities are basically the same, I briefly checked them out and didn't really hear any difference, but I heard from a good authority that the new N-26II's sound basically the same as the N-26's.
Maybe Phil I. will see this thread and give you the lowdown.
I really hope the wood enclosures make em sound better. I was comparing the N26s to the N28s at Best Buy and I really preferred the sound from the 28s. I'm not sure if it was all because of the enclosure but wood does make a better enclosure than plastic.
A lot of engineering went into the N-26 (plastic and all), I don't think the plastic enclosures are detremental at all to the N-26, if it was I think they would have opted for wood/fiberboard, JBL probably would have saved money going with wood.
Besides the way I understand it, the N-28's and all of the Northridge use the plastic waveguide design surrounded by wood. So by design the Northridge probably sound better with the plastic waveguide, and the wood is just a cosmetic thing.