Tested: Dr. D NS-4 Full Exhaust System SS/AL KX250 (Product Review)
Overall a really great exhaust system. It increases performance where the bike needs it the most, has robust construction, great fitment, is easily rebuildable, improved looks over stock and sheds a little weight while it's at it, all for a minimal price (in the 4-stroke exhaust world).
It's cons come from what it's not trying to be; exotic. So don't read that as a bad thing. For just shy of $640, it's hundreds of dollars less than some of the Titanium systems on the market, so expect the difference in price to be reflected in terms of sheer beauty (think Akrapovic) and weight.