Sizing a single turbo with more CI becomes difficult, you have to go to a large frame on a motor that would make 500rwhp NA. At that point packaging (aka, hanging a 60lbs turbo) becomes an issue for a street car. Granted you could undersize the turbo and destroy the motor/turbo in short order, but what fun is that.
If you go to a larger CI engine the best option would be a twin setup (like 35's).
Spool up and a broad powerband with a larger single isnt an issue if its set up correctly. I have a large frame 88 with a 1.06 exhaust housing on my "tiny" 357 and I see full boost in higher gears by 3500 or so. Granted in first it doesnt do much (its a 5 speed car). With an automatic and the correct converter it would be an issue at all.