I have a question. I'm a newbie and I'm getting a 350z next year. Well my dad is getting it for me to show me his appreciation of me doing my time in the navy. Anyways I was just wondering if i could replace the subwoofers with an aftermarket brand without it sounding like crap. I've test drove the car and to tell you the truth the factory system in the car sucks. I was looking at Soundstreams Tarantula series but i don't know what the airspace is inside and if it's even sealed behind the seats where the speakers are mounted. If anyone has any knowledge on this topic please help. Thanks for your time.