3" pipes are great if you want to maximize output for big numbers, but are you really going to go that high? What are your realistic WHp goals?
I can already get to about 470 WHp on my HR-TT with 2.25" exhaust no sweat. I've been in a VHR-TT with 3" pipes and I will tell you that it is loud (to me?), especially when it is started up cold. Just some things to think about if your Z is a daily driver.
@XwChriswX: IMO, do the 2.5" now and enjoy them. No rush to do forced induction until you are sure you are ready. If / when you decide to do so, you can easily get 500WHp out of them.
