I've had two sets of exhausts cans and link pipes made for my Raptor 650.
One was from MHP in Bisley, Surrey and the other by Blue Flame in Skelmersdale, Lancashire.
I have yet to use the Blue Flame system but both appear to be good quality and sound great.
If I was going out to buy a new exhaust system I would probably go for one of these:
http://www.redracingparts.com/en/eng...aptor65001.htm
The 650 also benefits from having an extra link pipe added to the standard headers as I have yet to find anyone who actually makes headers for the Raptor.