You said you like your bike. Why are you upgrading it? Just for the sake of upgrading it, or are there parts you're unsatisfied with? IMO cranks are a throwaway upgrade...you'll see little performance difference, unless you hate your triple and want to go to a single + bash or something like that, and even then, you can just play with rings. And I wouldn't bother with upgrading front derailleur unless yours is broken. Saddle and bars are most certainly not just aesthetics if you change them to something that fits you better, but if the bike already fits you well, they're fine. If you actually do dislike all of those parts, you're better off buying a new bike.