Nav: I used a TomTom 720 nav before I got my Z. It's got a better interface than the built in nav in the Z. And like someone else said here, nav apps for your phone are overtaking the stand alone nav units anyway and will come with far more up to date maps (my 7 year old neighbourhood isn't on the map!).
Stereo: The Bose is nice enough, but it's not killer. Besides, there's enough road noise that you're not going to be too fussed about hearing all the detailed nuances of your music of choice. A new HU with some nice enough speakers that you can turn up without distortion is all you should really need to look for. Having the integrated nav and iPod and bluetooth is nice, but an after market unit will get you all that easily. You could even throw in a rear camera and make it real slick.
Sport: I've got the touring with both the sport and nav package, and I'd say the sport gives more bang for the buck. I love the sport wheels and the look of the spoiler and I'm a fan of the rev-match. If you wanted to buy after market wheels, brakes and the spoiler later on, it's going to be a lot of money. If you can live without the leather, go sport. Easy decision IMO.
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2010 Carbon Silver / Persimmon, Touring 6MT + Sport + Nav + Tint
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