You dont want to go screwing spikes into speakers. Id try big blobs of blu-tack between speakers and the rack. Cheap as chips too!
Systemdek IIX, Arcam Alpha 7SE, Arcam Alpha 8R, Arcam Alpha 8P and ATC SCM40s. Philips 42PFL7404H, Virgin V+, Cheap DVD player till more Blurays I want become available.