Some speaker companies provide an extra spiking kit (like axiom) which contains spiked screws which can be adjusted to allow the speaker to lean back, so the front spike screws are higher than the back. They claim it improves sound. I think it does, but I know of one good sounding setup (an expensive setup with bass traps and stereo separates) which does not utilise spiking kits or even the toe-in.

It does look slightly cool though.

Clovis de Cruz