*All of these are from my own personal point of view.*
I love Silverstone II and I think the CF roof stands out nicely, especially when the light conditions change constantly. Looks really nice. People are always asking me "Hey, what color is your car, I haven't seen that before" and the like.
I've seen many Alpine White cars, and I personally think they look really great. But when 9/10 cars on the road are AW, the color doesn't turn *my* head like it used to. Still looks stunning close-up though, no denying that.
I haven't driven the M-DCT so I have no right to flame it, and I won't. But I grew up driving manual cars, then got stuck in an automatic for about 3 years, and I deeply missed the stickshift. So when I ordered the M3, I opted for 6MT. Personally, I love it. If you are asking about the DCT and saying that it's a big change, then chances are you might start missing your 6MT later in the future. DCT I'm sure is awesome, since people advocate it like a religion around here. But still, *you* might start missing the manual transmission.
Ok, see, I was cheap here, and I opted for the stock sound system. I have now sat in 2 other M3's with the enhanced premium sound, and I have to say that they sound much better. Is it overrated? Maybe. Overpriced? Maybe. But better than the stock? Yes. How much it is worth to you just depends on you. Some people say its not worth it, some people say its just not good enough. The former group probably doesn't care as much, and the latter group possibly has custom high-end sound systems in their vehicles to fit their auditory needs.
Now, is the stock system BAD? No, not at all. But would I have personally wanted more? Um, maybe.
If you like your music a lot, and have no plans to put in a custom system, then I'd say go for it. Chances are, if you're asking, then you won't regret getting, but may regret not getting.
Sorry for the long post. Nothing better to do today.