Well, Frank at Prodigy was right, I didn't like the Spintech mufflers. The interior resonance was way too much. I yanked them out this weekend and installed a set of the new Corsa dB mufflers. The car sounds amazing, has a great sound at idle, no interior resonance at any speed, and they sound wicked at WOT. I'll get some hole shot, WOT, and fly-by video soon.
Here's what it sounds like at idle:
www.lateral-g.org/temp/Corsa_idle.wmv