Dspeed

Afternoon all, go no joy in general so thought I try here.
I currently have a full scoobyworld afterbuner vortex system on my scoob and dont want to change it really. But its too loud for track days and the bung when used on the road is costing me around 30 BHP.
So Im going to buy a second back box as changing it only takes 5 mins anway, so what it the best performing and quietest back box on the market today for a classic?

http://photos-d.ak.fbcdn.net/hphotos..._6187324_n.jpg