Tbh I wouldn't spend too much on an induction kit for the noise. You're better off spending the money on the exhaust system imo to unleash the V6 noise.
I bought a Stillen induction kit (£250 odd) for my 350 when I had it and the noise increase was barely noticeable as it was mostly encased to avoid heat soak.
Take a look here for some of the options available to the 350 owners: http://www.tarmacsportz.co.uk/products.aspx?CategoryId=dd876c45-6d4a-41df-bc25-7c19903fe703
Most popular option, in part for the sound but probably because of the cost too is the "pop charger" induction kit. Link: http://www.tarmacsportz.co.uk/GB/350z_03-06_JWT_Popcharger_Intake/350Z03JWTPOP_.aspx