Where in the US are you? So Cal is teaming up to get board A/V guru bigaudiofanatic out here to do some installs. His basic but good upgrade
New to 370z with questions (buy at Amaz*n/Crutchfi*ld) is a good start. Subwoofer would be an option and not hard to add, but cost would double on parts ($200=$400 or more with sub and box).