There is no good reason to use any kind of maple or other block under your speakers on a concrete floor.
Some people use them to help isolate the speaker from exciting a suspended floor- e.g. a wood floor.
My system has always been set up in a finished basement, dense carpet and padding over concrete slab.
All of my speakers are spiked through the carpet to the concrete.
FYI a 205 lb speaker with four spikes will present a 51 lb load to each spike - nothing to worry about unless you use the speakers as pile drivers.