Best products for baffle material s ?

Daedulus, Rodman makes a valid and very interesting point. Serious woodworkers will know it "wood :-) " be virtually impossible for cabinets of different wood species to react the same to the drivers so they 'wood' all sound different!

"09-08-14: Onhwy61
I don't know the answer to this question, nor do I even have an opinion, but will the B&Ws sound better with a less resonant cabinet or will they just sound a little different?"
That's an excellent point. Whoever designed the speaker had to make it work with the original materials. Even if you go with a better material, there's no guarantee that it will sound better.

@Ptss- Some points about Corian; it can worked exactly as
wood(routed/dadoed/sawn/dove-tailed), but should be worked
somewhat slowly. Drills and taps nicely, for mounting drivers
with machine screws and/or clamps(obviating the need for T-
nuts). Dupont makes colored acrylic epoxies, specifically for
Corian, that can be used to layer sheets to whatever thickness
you desire, or to make visually seamless joints in a cabinet.
Unlike wood; it can also be thermoformed, if(for example) you
want to create a curved baffleboard. Versatile stuff!
(http://www.homedepot.com/c/BP_Corian)

Thanks Rodman, very interesting about Corian. I like the idea of a curved baffleboard -but-Peter of PBN mentioned the crossover is designed around the precise dimensions of the baffle and I wonder if that means it should also remain flat and square? It's very good to hear it can be built up.

As long as the internal volume and acoustic centers of the drivers remain consistent with the original design; no negatives should arise. Only reduced diffraction, from the baffle. That's hoping that the system was not voiced to compensate for cabinet resonances. To me; anything the the cabinet adds is editorialization and colorization. I don'r want my cabinets adding anything, of their own, to my music. Of course: many appreciate those additions. Diff'rent strokes, etc.