Amazon offers the Auralex GRAMMA Acoustic Isolation Riser for $49. Clip the $10 off coupon on the item page to drop it to $39. With free shipping, that's the lowest total price we could find by $10, although most stores charge at least $63. Measuring 23" x 15" x 2.75", it supports up to 300 lbs and is used to decouple instrument amplifiers, subwoofers, and other speakers from the floor.