From reading the July 1986 Stereo Review article, those Fortes look like very good speakers (
@ski2xblack Thanks).
If I were to use the Fortes with a powered subwoofer, wouldn't it be a good idea to electronically limit the Fortes' lower end so that the 12" cones wouldn't have to work so hard and possibly self-damage?
Those speakers are conservatively rated at a high sensitivity of 93 dB, and are able to reach as low as 40 Hz with low distortion. For music, I don't see a good reason why you would want to add a sub woofer. Considering the sensitivity and low distortion, you'd have to pay a lot for a low distortion sub woofer that went an octave lower, about 20 Hz.
The article did say, "It sounded as though the speaker might have reached to 30 or 35 Hz, but, by design, it simply won't go to those depths". I don't see a reason why a high-pass filter is needed to further limit the low end of these speakers.
Try them without a sub woofer and then decide. If there ever were speakers that don't need sub woofers, it would be these.
The review article suggested using a 60 wpc amplifier.