Heavily loaded spikes can pierce small change. In Canada we go up to two dollars and I've tried them all. (Took out the toonies before they got holed, I couldn't stand to watch it happen.)
As of now I'm using Herbie's Large Grounding Bases, good fer a 450-pound rack, but they got me into an online fight with an audio skeptic. He said I couldn't be hearing any improvement over quarters and furthermore they cost snake oil prices. So if you do choose them you might want to keep it quiet.