The slate only cost me a tenner, as I went to a place that makes stone, granite and slate fireplaces. He charged me the money to cut it to size, then bevel the edges, before polishing them. Looks cool, so got another one for my cd player in the lounge as well.
Stick some foculpods under the 4 corners, and you have a very solid isolation base for your kit, without paying a fortune!