There is a review of the Infra 12 in the November 2004 issue of Ultimate AV. The author, Robert Deutcsh wrote this quote:
"The Infrasub-12 does very well with music, providing an almost ideal blend with the main speakers, but it neither goes as low nor loud as its senior sibling, and there are some less expensive subwoofers around that perform as well or better in a home theater context. At $849, the slightly bigger Hsu Research VTF-3 plays louder than the Infrasub-12 and its low-end extension is comparable."
Does not help you directly with the Paradigm or Velo, but might give you some frame of reference. (The VTF-3MK2 is even less expensive now)
"The Infrasub-12 does very well with music, providing an almost ideal blend with the main speakers, but it neither goes as low nor loud as its senior sibling, and there are some less expensive subwoofers around that perform as well or better in a home theater context. At $849, the slightly bigger Hsu Research VTF-3 plays louder than the Infrasub-12 and its low-end extension is comparable."
Does not help you directly with the Paradigm or Velo, but might give you some frame of reference. (The VTF-3MK2 is even less expensive now)