Re: upgrade for a '05 E90 pre-fl
save the money for scheduled and unscheduled maintenance? after all, its a 6-7 year old car and you do expect more wear and tear parts replacement as the car ages (I own a '05 E90 pre-fl too).
I find the stock brakes very decent, not exactly as biting as my previous R32 brakes on my puny 1.4l golf gt, but good enough to stop in time for most cases. I'm not too sure if it warrants an upgrade from a performance perspective.
Cosmetic parts are generally more affordable and you won't feel the pinch when they go with the car when the COE runs out. e.g. front splitters, aftermarket front grilles, eye lids, etc.
Just my 2 cents. Enjoy your ride!