I drove the second coil via 2 unused channels on a multi-channel SS amp, through an ICBM crossover for about 7 months. I did notice some more depth on the bottom end, but not the WOW factor that I experienced when I switched to a Velodyne DD-15 subwoofer. The sub integrates beautifully with the Gallos. The bass is tight and visceral both in music and HT. With the upcoming introduction of the Reference AV (basically the upper half of the Reference 3s, if I was making the decision now, I'd opt for these smaller, more versatile units with a sub.