I am using the same size Granite Block myself,Its actually a Starret measurung block 20x20x3" and I have tried both.I depends on what your looking to do.With the Vibrapods the sound is warmer but has less air and definition,than with spikes.Using BDR racing cones , are somewhere in the middle of the Brass spikes and Vibrapods.My system is all tubes,so for me I stayed with the Audiopoint brass spikes under my cd player..You really need to experiment to really find out for sure.It really depends on your ears and what your loooking for.There are also many other variations of footers to use......Good luck