65 watts might not be enough power for a subwoofer, which typically requires the most power of all the speakers in a HT. It may also ask too much of the receiver. You might query the makers of the passive subs you have in mind for their recommendation regarding minimum drive power. A powered sub is never a bad idea, as the internal amp is perfectly matched and frequency compensated for the particular driver employed.

It is generally not as critical matching a subwoofer to speakers made by a different company. The problems arise when using a center speaker made by a different company than made the main left and right ones. The main thing to keep aware of is the respective low frequency roll-offs of your main speakers, and if that will mesh well with the high frequency roll-off of the sub. Again, the manufacturers can give specific info about this.

[This message has been edited by soundhound (edited January 11, 2003).]