IMO, the only time resonance is an issue is with the top up, it's as if the top creates a echo chamber. I had a Dansk SS and I thought it sounded awesome with almost no resonance.
looks like they redesigned them and gave the price a nice hike too, mine was like 1000
http://www.********************************************.com/Porsche-986-Dansk-Sport-Exhaust-srch.html