youre shooting for way too high of a number.
its hard to get a ka to 300 hp reliably with a turbo.

if you really want to go all motor, swap a sr20de, it has a better power band, and do a full build.

youll wish you spent the extra 75 a month by the end though.

edit:
you dont even own a 240 yet, but you have all these outlandish goals already set. any reason why you feel you need 300hp?