If you're sure it's from 2005 or 2006, I'd say you have 3 possibilities:

Most likely (based on looks, and stem) http://www.cannondale.com/bikes/06/C...del-6RR9D.html
Second, based on color: http://www.cannondale.com/bikes/06/C...del-6RR8D.html
And final, based on looks http://www.cannondale.com/bikes/05/c...del-5RR1D.html

Specific component list on those pages, and the 2006's list Fire stems (05 not), but neither fork is called "aero" so could be a swap. Just my thoughts...

Any other stock parts you can list would help narrow it down easily. ie, if that FD is stock, what is it? same with seatpost. Actually all three listed above have different front derailleurs. That could well answer it.