Velodynes with servo control are great, but watch out for the earliest version of the HGS-10. Mine is the early version and is working great after 6 months, but a lot of people at Audioreview had major failures. The HGS-12 didn't have as many problems. The bigger Hsu seems to be a great sub (check out the Audio Critic review), but it's tall and tips over easily. It's hard to hide. My Velodyne is an 11" cube that goes anywhere. In a normal size room a HGS-10 is plenty. I listen mainly to baroque chamber orchestra,organ music and The Who. It's only down -4 dB at 20Hz at my listening position. 20Hz is clean without doubling;it knocks dust off the ceiling fan and cracks the walls.