For looks and sound, definitely get cat-back exhaust first. Spacers with Springs or Coilovers will also make a big difference in looks. Don't forget to factor in installation costs if you're not doing it yourself.
I wouldn't bother with an intake unless you want to complete your performance bolt ons.
I wouldn't cheap out on Wheels/Tires so I'd save that for the next time you have $4k to spend. The same goes for a full body kit or lip kit, more if you're needing paint and installation.
__________________
SOLD 12/30/2011 2010 370Z Coupe Monterey Blue 6MT/Touring/Sport/Nav
F.I. CBE CF w/ 12" Res | V1 | SecondSkin | Stillen G3 | EVO-R CF B-Pillars | Volk GT-S Ti Gunmetal 19x9.5 +30 F, 19x10.5 +8 R | Swift Spec-R Springs
|