Borla Exhaust?

i was looking at exhaust systems for the E46 BMW M3, and i was looking at the Borla Catback exhaust, but i was wondering...what is the best exhaust system for sound and hp/torque gain?

i have looked at the Borla and the Active Autowerke systems, and both are pretty good, but i know there are better, but i forgot.

Dinan, UUC (which I've herad sucks), and if you got the money, RE offers a system from Japan that looks and sounds real nice, but it costs quite a bit.

what does RE stand for?

Rouge Enginering