I own a VTF-3, have heard a VTF-2, a SVS 20-39PC+, and Hsu's cylinder, the TN1220HO.

The 1220HO is the best performing out of the all them. I thought the VTF-2 and VTF-3 were clean and tight. Well that TN1220HO is even cleaner and tighter....and has slightly more output at 16hz than the VTF-3 when used with Hsu's 500watt amp.