As others have said, changing the subs would be good.
The sub choice is yours >> however, I will say for one on a tight budget,
and who listens to mostly music, that the Jamo sub does look interesting.
I am waiting to see more
Jamo Sub 650 Omnimic Frequency Response Graphs
You do have some good choices on your list, and another decent one is Epik
And for a tight budget and needing 2 subs - the Energy S10.3 is a nice one,
and it will go down and is not a wimp. It is good for music and H.T.
Newegg.com - Energy S10.3 Subwoofer Each