yeah. There's the rub. Around here marble, granite, and one other I forget the name of now, aren't real expensive per precut piece. The problem is and I suspect they know it too, is their idea of precuts ain't my idea. Hence ya gotta have 'em slice and dice up whatever dims you need/want. Black marble, runs around 180 - 200 cut to 14x14 last time I checked, and that was a couple years ago now. I shudder to think what it could be now....
I wonder if they would or even have, a couple pieces which I could rent to try out... hmmmm. I never thought about that part. I think I will ask. Sure, if it is a good move, I'd go off for two pieces... cut and polished.
I wonder too, just how thick ya need to go with rock platforms for speakers anyhow?