Should I spike my B&W 804D's

If it is through carpet to a cheap wood substrait, yes spiking can gain a solidity not otherwise found.
If the speaker is already directly ON a wood floor, then spiking may not do much (except damage the floor) ((solveable by using a base ten spikes to speaker. find a 18" by18" or so solid wood base, lay it on top of flooring then spike the speaker to the base...??))

I too have been considering this. I am using a pair of Snell B minors in one room that are on the hard wood floor. In the other room I have a pair of Montanas that are on the wood floor. Neither pair are currently spiked. The Montanas have the cast iron platforms.
When I attended the Capital Audiofest the guy from Mapleshade was saying I should be spiking the speakers and placing them on their wood platforms and place the platform on the rubber squares.He even went as far as to say I should remove the sttel platforms from the Montanas, said I would get way better sound and bass. Not keen on spending the $1000 for platforms and spikes and rubber squares. Thought I might try the maple platforms from Dawnsplatforms. Any body try them? The rubber squares aren't too salty from mapleshade.

There are brass discs with a depression in the center that are sold so that you can use spikes by putting the tip of the spike in the depression and not damage your wooden floors, if you don't have a lot of drunken parties at your house.

Vibrapods...try 'em...be like me.

thanks for the insight guys. I am hesitant to mess with it too much. It is already sounding really good to my ears. I'm just always trying for that last little tweak. I fear I am at the point of diminishing returns though as far as speaker setup goes.