Does a Subwoofer Make Spiking Redundant?

i read a lot of this and find it confusing. certainly contradictory ( what else is new?).
There are many theories, but the most reasonable, to me is that we want speakers to be totally immovable - a solid, stable surface for drivers to push against.  If they resonate, they modulate the drivers - especially the midrange and tweeter where the wavelength is smaller relative to any vibration or rocking motion.

Spikes are often used to cut through a soft, unsupportive material that will allow the speaker to rock, such as a carpet.  The subwoofer OTOH adds lower frequencies and is mostly an orthogonal choice.

Now, a spike on a hard surface is a different animal and I would tend to not use them. Those spikes minimize the surface area (which in the newtonian sense of friction m,akes no difference), but also increase the force per unit area meaning the connection will be more fluid due to material shear. In theory. This is why car tires are non newtonian as well (wider is in fact better).

I prefer mass to stabilize the speaker (big, heavy speakers on a solid 3-points so they don't rock) and maybe as one suggested actually isolating the speaker from floor vibrations especially if its a live floor. I have not experimented with those.

My speakers are spiked, heavy carpet, pad and plywood underneath.
   If I place on rug, they are tipsy.

The job of the spikes is to pierce the carpet. Lose the plywood and pad.  But you may leave a mark on the underlay if it is hardwood.

OP misunderstands the reason for spiking. It is to prevent the whole speaker moving around and adding that movement to the signal driven movement of the cones etc.

right. A different way of phrasing what i wrote above.  It is modulation.