@testrun The only reason you need amp stands is to get the amps up off the carpet so that they ventilate correctly. I made a set just recently and used 8/4 walnut on spikes. You have to finish the wood which is more expensive than the wood. Stone is more difficult to mount spikes on, but does not need a finish.
As far as sound quality goes it makes absolutely no difference. If it looks better to you it will sound better. So, by all means, pick what looks good to you.