With that sub you will probably only need 3-4 springs per footer. This will leave you with 12-16 springs left over, enough to make another set of footers to use under another component. You can make additional footers from MDF, acrylic or wood. Drill some 1/4" divots the way Nobsound does to hold the springs.
The improvement from under the sub will be okay, not nearly as much as Townshend Pods but at least as good as other stuff mentioned. Combined with using the extra set under a CDP or whatever you will find hard to beat for $30.
You do not by the way have to put them under the existing factory feet. They can be used just inboard of that, and with a spacer can wind up with almost exactly the same height above the floor as now.
The improvement from under the sub will be okay, not nearly as much as Townshend Pods but at least as good as other stuff mentioned. Combined with using the extra set under a CDP or whatever you will find hard to beat for $30.
You do not by the way have to put them under the existing factory feet. They can be used just inboard of that, and with a spacer can wind up with almost exactly the same height above the floor as now.