What isolation feet under your amp with great result?

I had very slight woofer pumping when I was using my Manley Chinook phono stage playing over 80 decibels. I bought a Pass Labs XP-17 phonostage & the woofer pumping was out of control even at mid volume levels.  The floor to ceiling drapes behind the speakers were moving. I tried everything to contain the pumping because I liked the XP-17, but with no success. I then purchased a T+A phono stage (amp is T+A) and have no woofer pumping from playing vinyl. Sound is also even better. System synergy between matching components prevails.