Mine has the dual Librands system and trust me this is not a decision to put off, at +/- 1,500rpm the popping away on over run is enjoyed by all.
It really barks when you floor it too, as has been said the side pipes get tiring. Long distances are at an acceptably enjoyable volume with mine.
I don't hear any advise from the navigator with the top off so it's all good
http://www.librands.co.uk/products-view-96.htmlGood luck with whatever you decide.