Looking at putting together an upgrade list for the girlfriend's Z. Nothing crazy, but good quality parts and clean. Would like to keep this around $5,000-$7,000.
2006 350z
Daytona Blue
Automatic
Just under 60k miles
Stock all around other than we plastidip the wheels to see how they looked black
Current ideas to upgrade (and need help on brands that are good/bad):
Exhaust - Does the 350z have the hiss when you upgrade the exhaust?
-OEM is pretty good sounds already, do you need to upgrade it?? I believe about $1000 you can get Invidia or ARK, I am using ARK on my 370z and it is 
X 2
Plenum Spacer
Intake - Nothing which might cause the intake to soak up water
-Short Ram such as K&N, about $330
Wheels - This I need help on sizing & offset, will stick with 18" & probably something black
Brakes - Plan is to give her my OEM BBK, what do I need for this to convert it for the 350z?
Head unit - This I will probably go with a Kenwood as she likes mine but probably something a little cheaper
-Kenwood DDX-719($499) or DDX-419($349). Unless you need GPS, otherwise both are
Besides this I am planning on some good maintenance, automatic check, radiator, injector, etc. inspected. Just last week ran into a major issue that one of the tires that was on the car when she bought it was falling apart. Have to love used car dealerships who put the cheapest (possible used) tires on a car.
Any other suggestions or thoughts I need to look at with this car?