This is probably going to confuse the issue but mine is the newer one and it sounds very similar to mark's. BUT the centre section gave up after the last airfield meet. (rattling, tacked not welded apparently) The replacement middle box was a different shape.
I dissagree with the comments about wet fart, raspy sound. Mine was a little to start with but once its coked up after a 1000 or so miles it matured, I have had many positive comments about the sound. You will have to hear one, I didnt but i needed one QUICK so took a punt and im pleased with it.
Shame your a bit far from the airfield meet to come alog and listen to mine and Marks
Just had my third k tec stealth system fitted saturday morning must say new design is a massive improvement much quieter and car feels smoother to drive excellent!