Dude... I can attest to this... the AEM intake is absolutely the best intake available for the coupes fitment wise (V6 that is... I don't think they make one for the QR). The MAF bracket doesn't point at the top of the hood like on the Injen (that just bothers me... I don't like the MAF plug being so exposed like that... plus every installation I've seen makes it look like the wire is bent pretty dramatically). You really do get what you pay for with these things... they say you're paying for a name, but you're also paying for professional R&D and professionally built parts. For me, it's all about peace of mind, but you can spin it however you want. I also go by a statement I've found to be very true with most purchases - "Cheap buys twice".
For an exhaust, I own a Tanabe. I find it to be a very clean look, AWESOME fitment, and not too loud. On the other hand, Stillen catbacks seem to be the all around best bang for the buck when you compare all of them. I was honestly sold on the look of the Tanabe, which is most of the reason why I bought it. If you're looking for something simple to install to give you a bit of presence, Tanabe. If you're looking for something like the Tanabe but louder, go Borla. I think Stillen has the best bang for buck offering for a catback. But if you're not caring about cost, the Greddy Spectrum Elite is just pure sexy!
Wheels are purely a taste thing. At the end of the day, get what's gonna make you happy. Just make sure they fit well haha.
Lowering is something I've been studying a TON lately, cause it needs to be next on my list. My big concern is my car is my daily, and it gets driven a LOT. I'm still weighing between the two (springs or coils?). Tein costs more, but is a solid brand. I might wait and spend the extra cheddar on their SS coilovers. Although, apparently the Basic Damper systems are coming out, which will be cheaper, but you can't adjust dampening. So if you don't like the potential harshness of the ride, you're stuck with them.
Anyway... mod it up, dude!