@thielrules, while I agree with what you've posted, I think there are few things to consider.
The 3.5's as supplied only have single amplifier inputs. What you are suggesting is not possible without modifications to the speakers, which could depreciate their resale value. Sending a separate signal to the eq and then to the woofers, and a separate signal to the rest of the drivers could present a time lag to the woofers compared to the other drivers. Time is after all really what makes speakers like Thiel different and special. Of course in the digital domain it could be compensated for fairly easily, but in the analog domain, well that might take someone like Jim Thiel to figure that out. Also, 6 dB may not be much compared to say what a port rolls off, but it still is rather significant. That 6 dB is per octave, and there are two octaves to cover.