I run a twin turbo 486" Ford. @ 7lbs of boost I've got 700 hp. The problem with turbos is getting them proped right. I use a 27" Mirage prop cupped out to a 29" Much more prop and I could barly get on plane. Boost starts to come on an 3200rpm. I set my wastegate at 6.5 lbs. I can spin the engine way past peak hp, so I set the rev limiter at 5500rpm. I know I could be fast ( I run low 80's) or have a better cruise (3500=40mph, I think). But I'd have to do a lot of tricks to get up on plane.
I think with the new turbos , you can get boost building a little sooner. that would help. Even 200rpm sooner would help.
I love the sound of the turbos whinning, they also keep the exhaust quieter at low rpms.