I had a pair of Brightstar's BigRocks under my Dynaudio Contour 5.4's for quite awhile, but then found better use for them, one under my turntable, the other under my uni-disc player, where they actually made a discernable difference. At least in my situation, yours may vary. Solid maple risers would be just as, or more expensive than the BigRock's. I've heard of folks using solid Granite with excellent results claimed. Maybe you can do some experiments using different materials to see what works best.
Good luck,
Dan
Good luck,
Dan