The 2530 is your best option if it's open to you. I went a different route and had a custom built turbo made to cater for my needs, but I was chasing big power.
The RB20 torque response is a pain in the butt due to the short stroke, but if you get the combination of supporting mods, gearing, and driver technique right, you will easily achieve the power figures you are chasing.
Good luck man.