I experimented with the above pad and Tuned Feedback with all various settings of amount and tuning. It does add a remarkable growl, alright. It's an impressive sound to sit and listen to, rumbling and roaring till the floor shakes. The all-important musical effect, however, is that it limits you to octaves and fifths, and even these become terribly caustic. Triads and seventh chords are out of the question. A major seventh would shatter the windows, and a tritone might have the same effect on your skull! The delicate soft sections of the piece are also corrupted beyond use. Plus, as you adjust the tuning, the fundamental falls away and the tone becomes hollow, like a flanger.
A fascinating experiment, but it's not my cup of tea. I realize this is one of the primary reasons people like the Evolver, but I like the instrument for other reasons. I'm not a noise/sound-maker, but a musician and a purist. I much prefer the deep warm musical ambiance of the original patch, without Tuned Feedback or even Audio Mod. So, I could certainly conceive of using the effect for a note or two as a means of creating an impending atmosphere, but not beyond that. Much more appealing was adding a lot of Glide to all the oscillators, which made the slow lumbering changes of bass notes quite a bit more dramatic.
Anyway, it was an interesting experiment. Thanks for the suggestion, Dslsynth.