I too am in the market for a pipe. I have an 01' kdx 220. I've called 3 or 4 different companies and all three recommended the Pro Circuit pipe over the FMF, for my 220. Apparently most MX race teams, including Kawasaki, run the Pro Circuit.
I was told the FMF Gnarly helps low to mid but loses on top, rev pipe helps mid to top but doesn't help low. SST helps over all, but with "recommended" matching silencer, costs $380.
Pro Circuit helps over all similar to SST, for a lot less money.
rockymountainmc.com (1-800-336-5437) was by far the cheapest. I ordered one today "Pro Circuit Platinum" for $144 and a spark arrestor for $99.
Hope this helps.