I've got a Rel Stadium III which is downward firing. It is currently spiked on carpet which is laid over dense rubber underlay on a concrete base. Question is - Would it improve the performance if I stood it on a marble or slate slab. The spikes probably go through to the concrete base but as it's downfiring would the carpet muffle/absorb some of the shifted air altering the effect. Also, how does this sub compare to the SVS subs that are getting a lot of discussion lately.