I agree with KC, having used both the presonus firebox and Apogee Duet... and liking them both, I'd go for the Duet. Especially considering the Firebox needs to be plugged in to the mains to use with macbook pro's now... making it not as portable as it once was :(
Depends what you are looking for in an interface? Do you need mic pre's, xlr, how many outputs? etc.