If you are going to upgrade your sub, make a significant improvement. Both the Paradigm and new VTF-3 will offer minor improvements over your current VTF-3. If anything, add one of these subs to your current VTF-3. Otherwise, save up your funds and get a sub that will offer a significant upgrade in performance.
Perhaps some room treatments or a parametric EQ would be another sub performance-related option?
Perhaps some room treatments or a parametric EQ would be another sub performance-related option?