Cornwall IIIs: Frequency Respose 34Hz - 20kHz
Right off the hop the listener is missing out on 24Hz of the music spectrum.
As I stated in my post "If one purchases a pair of speakers and you have to add bells/whistles, subs, and modify (although I am an ardent advocate of mods), perhaps it's time to rethink your choice".
And what do you say? "a couple of RELs to make things outstandingly good". So now your taking up even more space with the RELs/ Heresy than you would with the Cornwalls, plus, now you're dealing with phasing issues. You also go on to say "and the price difference alone would allow the purchase of a swarm of woofers". That's economical isn't.
You're saving nothing, taking up more space, introducing phasing issues, why are you trying to make a silk purse out of a sow's ear?
If you'd re-read what I wrote " Heresy's are not a bad sounding speaker", " The Cornwalls are such a better platform to build on".
To close the Cornwalls are easier to drive, 102dB, as opposed to the Heresy's 99dB, plus you get a 15" bottom end driver as opposed to the 12" that comes with the Heresy, not only giving you a wider frequency response, but also fuller richer sound engineered right from the factory .