I found that removing the bottom rails (on HD requires a square-driver) and replacing rails and spikes with Black Diamond Racing's Super Jumbo pucks gave great sonic results and a very stable footing for the speaker.
If you are still looking for better quality spikes, etc...you may also want to look at the heavy spikes and other items sold by Mapleshade...
If you are still looking for better quality spikes, etc...you may also want to look at the heavy spikes and other items sold by Mapleshade...