To get the best bang for your buck, look elsewhere... unless you have MAJOR engine mods, such as cam and porting, there is no need for higher RPM limits or any other features an aftermarket CDI provides. Aftermarket coils do almost nothing, period, regardless of mods.
Put your money into exhaust and air intake mods first.
near the top middle of the page are the words "User CP"
click on that, look on the left hand side of the new page under the "settings and options" section heading.
Click where it says "edit signature".
type what you want in the big box in the middle of the page. scroll down to the bottom and click the button that says "save signature"
I don't know what a "pop up piston" is, but from your mods I would suggest a port job as the best way to spend a few hundred dollars. There's nothing you're going to be able to add for cheap that will dramatically increase your HP output. But some stiffer springs for the clutch might be something cheap to help you put power to the ground.