The outriggers look like they should have some kind of pad, to prevent them being the area resting on the carpet, especially with padding. Assuming the spikes use 1/4"-20 thread, you should be able to find rubber pads at a good hardware store. I just texted my friend who works for KEF and they don't offer rubber pads.
Also, I wouldn't remove the outriggers because that would allow them to tip far too easily. It's also the main reason they come with spikes- the tips penetrate deeper than a flat pad, so they're on the hard surface, rather than on something that's soft.