Dean, the additional power of those bigger turbos is pretty useless for autocross IMO. For example, I'm probably 30hp at the wheels more than Matt, Mike and Eric, and they've still got the power advantage over me because they have earlier and bigger torque w/ their stock turbos vs. my 20G.
I'd go with something smaller if autocross is your goal. Staying in BS might be a good idea, but PAX between BS and SM really isn't all that different.
If you're thinking of SM, I still have that SBR GT30-10 I'll sell you for dirt cheap... it'll spool faster than stock and make similar power. But GST Mike will hate you for having to tune a 2.5L with that undersized turbo again...
