The Greddy Turbo Ti-C will have no drone with the silencers in. It's a lot louder with them out and some drone right around 2800-3200 RPMs. 2.75" diameter pipes.
And gains about ~10whp/8tq with silencers with no turbo
It gains about ~7whp/4tq without silencers with no turbo
Pics of the fitment and quality here:
Nissan 370Z Forum - TXSpeedDemon's Album: Greddy Turbo Ti-C Exhaust
I'm real happy with mine. Sounds great inside and outside of the car. Looks good without being too big/showy. Fit perfect with no issues at all.