While not one of the big name brands I'm more than happy with the Thunder Alley system they made for my XR284. Fit was perfect, price was about the same as any other and the design gives better power across the board using my seat-o-pants-o-meter with significant gains in bottom to mid and top that the stock system couldn't dream of. Also available with a Kritzman spark arrestor option for a very reasonable cost. :thumb: :thumb:
A very popular exhaust is the Yoshimura full comp. system. There is lots of info. about it on www.thumpertalk.com. I own one, which I took off of my recently sold DRZ 400 and was very happy with it. The nice thing about them is the TEC inserts that fit in the end of the pipe; they can be changed out depending on how much or little noise you want to make. By the way I am selling mine on Ebay if you are interested.