I have profile design carbon strykes on my allez elite. I like them and think I pick up a bit of speed. I also like them for long rides when I am solo.
I'd say that aero bars are a worthwhile upgrade.
If you have $400 - $500 wheels would be nice too. WOn't be a night and day difference in speed but you'll like better ones. I think you can get Ksyrium Elites for about $450.