adding a sub to a bookshelve set would still be an upgrade. improvement would be the one in questions as the US Audio sub as I recall cannot go below 30hz properly.
alot of PDVD members also started using this sub, including me.
![Smiley :)](https://www.pinoydvd.com/Smileys/default/smiley.gif)
some still use it till now and still smile.
GO ahead and try it. experiment till you find your own likeness.