First: Dell Orto makes some of the best carbs out there. About 90% of the tuners i know use DO's. They're cheap, reliable and very easy to tune.
Your stock crank will not survive the TP Due Plus kit forever.
I'd say 2000 - 3000km at most, if you drive the bike hard that is.
And what that about 18000rpm? You'll never get a ~39mm stroke engine to rev that fast anyway. Piston speed would be way too fast and the piston would seize.
The TP kit is build for around 10 - 13k rpm max, depending on the exhaust.
If the Rieyus left you behind very badly, it's probably because of the setup or them not running stock TP 75's.
Oh, and more power without increasing the size of the engine always comes at the expense of more RPM and a more pipey engine.