Can't speak for the 350s, but I have 2 500s and the room shakes when it needs to (and they sit on the concrete foundation, on spikes).

LFR1100 Actives,QS10HPx2,QS8x2,EP800,M3x4,M3x2 (Wood),M5HPx2 (Wood),AxiomAir,ADA1500-8,ADA1500-7