A friend of mine tested one on a 2001 Cr125 and got exactly the same result as on the FMF website-1hp more from mid upwards.Its alot of money for 1hp, but if you have done the usual mods and you have the money then go for it.One cheaper option you could try is a 38mm carb.
very few mods will give you more power across the board so choose your mods wisely,it sounds like you are ready for a Eric Gorr 133/144 big bore conversion-about the same price as the ignition and if your 2000 has been ridden a reasonable amount it could probably do with a fresh cylinder.
FMF and Pro Circuit will give you a cookie-cutter job. Eric will tailor your mods to give you exactly what you tell him you are looking for. FMF did my cylinder, and I wish they hadn't.