I use 2 TN1220HO subs & Hsu's Model 500 Subwoofer Amp crossed at 51 Hz to augment the low end of my Magnepan 3.5R speakers. For 95% of the music I have listened to, the 1220's blend into the speakers seemlessly; the 1220's are very clean sounding and powerful, but not boomy, and I have had no need to turn the dial on the sub amp past the 9 o'clock postion; I have listened to a home theater system pairing Velodyne's top-of-the-line 18-inch subwoofer with MG 3.5Rs, but the Velodyne's boomy sound muddied and ruined the sound coming from the speakers; If you just want to shake the building, go with something like Velodyne, but for reference-quality bass extension, I find the TN1220HO subs worthwhile.