Ade,
If it were me I would run a similar setup to my 6, it sounds sweet (real V8 rumble especially with a blip on the throttle, just ask the wife she loves it) but it is not crazy loud and is perfectly reasonable driving at highway speeds with the roof down. I have even installed a radio and can here it easily.
I have the Headman full length headers running into 2 x 2.5" pipes running into a flowmaster series 40 mufler on each side, this then drops out behind the rear axle. I have approx 10" of pipe out of the muffler.