alternatives to spikes on wood floors?

Small metal discs that the spikes can go into to (a number of companies sell these). They will keep the resistance high and protect your floors. If you find the right spot putting them into the floors does yield better results, but at obvious cosmetic expense.

Another possibility is the Aurios. I'm using these between a granite platform and my Talon Khorus to good effect. Also tried Nordost pulsar points and DH cones, but like the Aurios better.

Another possibility is Polycrstal spikes (available from the cable co.) which would be a sonic improvement and will not make holes in your wood floors unless your kids use the speakers as skateboards-