I think well integrated any sub is worthwhile, the problem is the "well integrated" part is often a beast to achieve.
So, to quote the Bard, "what dreams may come must give us pause and make cowards of us all."
Start by measuring, and considering your room first. An untreated room may have far too much treble already. The room may be giving you a lot of bass in the wrong areas. Room treatment and careful EQ may be a better starting point. Use the AM Rock room mode simulator to help en sure your speakers and listening position are in the right spots.
If considering a sub, where will you put it?? The room simulator will help you find an optimal location.