The units go down to seventeen HZ. You do not need the subs. Ignore the reviewer comments concerning the subs on stereotimes.com, he stole the information from my uncle and tried to add to it (unsuccessfully I might add). The subs are great but I don't think the speakers need them. If you just want the added bass impact that is another story. I bought the speakers and I have heard them with 2 powered ROC subs. It is in my opinion over-kill, but...if it makes you happy that is all that counts. :) Mike