If that is true then you likely need to replace that sub. A good sub that still performs within spec should be capable of producing clean bass well above 60 hz. This makes me think there's something wrong with your sub.
That "punch" is going to come from higher frequencies than 60 hz and below. This is why I recommend trying a higher crossover. If your current sub can't handle it then I'd replace it and start over.But still, i would not try to overlap upper bass, but use the Legacy for only signals below like 50-60 for extra punch.