i personally like the SR20DET

phase2motortrend race car is pushing 474hp on 25psi with the stock bottom end.. they are going for 500hp pretty soon *drool* anyways, the s13 sr20's have T25 turbos on them. the s14 and s15 sr20's have T28 turbos on them. the S14 has a T28 ball bearing but the S15 has a T28 Ball Bearing with a cast divider wall between turbocharger exhaust flow turbine and turbocharger exhaust actuator wastegate flapper
i'm don't want to start another hositle discussion/argument, but this is what i would do.
option 1: get the sr20det
option 2: mod the ka24de
option 3: get the rb20det or rb25det
even though the rb makes a lot of power, it would be my last option.. just my 2 pennies