I have been told the cheapest way to get good bottom end is to have the head redesigned. $50 bucks +shipping +head gasket = great bottom end. I'm sending my head to O'Conner racing this week because I too am looking for more bottom end.
all i have to judge is gear and sound.but my kx powerband is a pain to get to im lacking bottom end so its a late responce.but my blaster was much beter in the bottom.like almost emediate.with a good lean and pull.. right up..id say 1/2 throttle with a high rpm.best i can say.