Running the sub from your headphone jack? Uh, no. If you're using a home theater receiver, it should have a subwoofer out. Use that.
Which input are you using on the sub? If you're using the LFE, try the left (line level) input.
As others have said, the "punch" you're looking for is more in the mid-bass. A sub is for lower frequencies.
I have owned a number of SVS subs and currently have a pair of SB-13 Ultras (similar to your SB-4000) in my 4 subwoofer distributed bass array.
The sub you have is by far the best component in your system. The sub is not the problem.
Which input are you using on the sub? If you're using the LFE, try the left (line level) input.
As others have said, the "punch" you're looking for is more in the mid-bass. A sub is for lower frequencies.
I have owned a number of SVS subs and currently have a pair of SB-13 Ultras (similar to your SB-4000) in my 4 subwoofer distributed bass array.
The sub you have is by far the best component in your system. The sub is not the problem.