Exhaust Poll

sinceday1

All or any of them you listed are good choices.

Generally, I do not think you can go wrong with any of which you listed. What might really matter though is your 'style' preference' and what you expect to gain from the exhaust.

Do you want OEM style canister that tucks and hides behind the rear bumper? or do you want dual canister? or do you want dual canister with helmholtz resonator?

Next is cost and waiting time.

Stock style: Most expensive to less expensive. (minus Amuse and other 3k+ JDM)
Berk (X pipe, US)
Stillen (Dual to Y pipe to Dual, US)
Exotic speed (X pipe, Canada)
Invidia (adjustable tips, X pipe, sub $1000 US)

Dual Muffler: Most expensive to less, (minus Amuse and other 3k+ JDM)
HKS (adjustable tips + Helmholts + JDM + H pipe)
Fast Intentions (US, X pipe, most gains)
ARK Grip (KDM/US, Helmholts, X pipe)

As far as gains go, Fast Intentions and Stillen seems to produce the most HP/TQ gain but differences are minimal at best.

Personally, I love how HKS sounds and looks. Authority speaks for itself. Daddy AK also has HKS

Also, following sticky post might be helpful to you.
370Z Exhaust Sound Clip data base

Cheers!