Redkiwi, for butcher block material check Professional Cutlery Direct at www.cutlery.com. The only blocks in the current catlogue are 16x16, but they can probably hook you up with any size you want ro have something cut to your specs. I would think that the "end cut" blocks would to the best job. If it doesn't work for audio purposes, you still have a nice cutting board.
Shelf Material
I have tried so many different shelf materials, and some are better than others, but I feel like I am just spraying bullets that always miss the bulls-eye. So far, I cannot live with the brightness of glass, the ringing of marble or granite, the sluggishness of acrylic, the muddiness of mdf etc. Light and rigid seems better than heavy and dense - in that I can live with the downsides more easily. I use heavily constructed welded steel racks - spiked to the floor and upward spikes supporting the shelves - and I reckon this is right. I like the way bladder products get rid of the resonances that plague shelves, but find that the way they slow down the pace of the music is hard to accept. Does anyone have some answers on this?