Unless you'r doing circuit work, if it was me I would keep with the 20 and basic bolt on's until the setup starts to hold you back (particularly if you're drifting), put a lot of focus into suspension. Generally, the better you can do on lower power the better your driving ability (that's becoming my catchphrase on this site).
Don't know what it's like in NZ, but a lot of Aussie's have the mindset that unless they have bucketloads of power they won't be able to drive well. This in turn makes drivers rely on power to compensate for poor ability and poorly setup cars.
Check out these two videos of this C33 Laurel in Japan. Pretty sure the RB20 is close to bog stock, but he uses his speed and inertia to get a pretty damn long line. He did say he didn't have time to get the suspension up to spec though.