Can you elaborate on what you mean by "almost no resonance"? I've been looking for a good replacement system and I really like the Fabspeed exhausts but have read that these mufflers do drone a bit unless yours is different. I've seen two different styles for 986 from Fabspeed, one is a single wide unit and another two separate cans, and I'm not sure which was reviewed in various threads.
I've also heard good things about the FVD. Here's a review on a new Boxster.
http://www.6speedonline.com/forums/boxster-cayman/196256-fvd-muffler-2009-boxster-s.html