Miltek on the 2.8 V6 is very classy! Sounds like a proper V6 outside and just reminds you it is there on the inside. I did however find it a little too imposing inside when it was hot from motorway journey, bit of weight in the back (I have the Avant) and under throttle, but a bit of sound deadening in the boot floor has sorted that out. I am over 40 though!!
The best part is that it cures your engines asthma, the engine not only sounds great it can actually rev now and becomes very spritely and a joy to drive. You can put it in 3rd and hold on 1/2 throttle and you feel the 3 power bands through the rev range right up to the red line. On the standard system I never went above 3k as there didn't seem any point.