Do I need a sub?

Would I benefit from even a small sub?

Energy rc-70s’
dual 6” woofs, bass is there, but would a sub remove the lowest freq, and give the small drivers a break, and sound better?

would it help,? I play loud once in a while, would the low freq removed from the main tower drivers make a better sound, I don’t think I would need much more than a 10 or 12” sub. 

Powered or unpowered?

thoughts?
thanks