EDIT:
Darn it, I read your post as FAST commuting bike, not FIRST. Well, I wrote all this stuff, so I'm posting it anyway. Maybe it will help even though it answers a question you didn't ask.

You are doomed.
Here's why:
You get a nice cross bike that's fast. I did that. I got a Motobecane Fantom Cross Outlaw with disc brakes. Cool!
But then you add a rack. Gotta have a rack for the panniers you need. Right there you move out of the fast zone. It's just like adding a parachute. A heavy parachute.
But you aren't finished. You really should have fenders, which add more weight and drag. Enough that you'll notice.
You'll want lights, and even though they are amazing now, they do add weight.
Your tires should be a bit tougher then nice road tires, and that translates to slower. You'll be happy you aren't fixing flats, but still, they aren't fast.

I love my commuter bike, but on the rare days I ride my Specialized Roubaix to work I get there a heck of a lot faster.


Motobecane Fantom Outlaw commuter bike by ccorlew, on Flickr