Subwoofer vibration foot isolators????

I have a SVS PB13 Ultra subwoofer(piano gloss black) and the feet are rather short(roughly 1/4-1/2 inch from floor). Can anyone suggest a vibration footer to raise the sub from floor(carpet) and be able to handle my 150 pound subwoofer to eliminate unwanted vibrations of the house. I tried different placements and the vibrations decreased by leaving about 2-3feet from the walls. I would like it raised off my carpet about another 1/2 to 1 inch more...I noticed 6 threaded feet on this beast....ALSO: basement room measures 18x23. Any suggestions!!!!!!!!