before you do anything--clipless pedals and some road shoes. sure, you'll lose the ability to walk around off the bike, but with such a flashy bike i wouldn't leave it locked up anywhere for any period of time (regardless of the type of lock).
that said, you will notice a huge (and i mean HUGE) improvement in your riding. no wasted energy on shoes flexing. there's a bit of a learning curve if you've never used them before, but its worth your time to do it.
i have the speedplay light action pedal and a pair of pearl izumi kicks (can't remember the specific model, but they're a few years old). i'm quite happy with those. they fit well and the pedals are very secure with good adjustment and float.
word of advice and/or oppinion, if you're trying to upgrade on a budget, spend more on shoes and less on pedals. its better to have a rockin pair of shoes that fit well with good adjustability (ie, a ratchet with velcro straps than just velcro) than have a stupid light pedal with shoes that cause blisters and hotspots.
as far as the rest of the bike, i wouldn't worry too much about the upgrading at this point if this is your first bike. just run it into the ground haha after you've been riding for a while and built up your knowledge base on cycling equipment, then you can decide what you want to upgrade.
seatpost, saddle and bars are a good place to go from there. the cannondale branded stuff weighs about as much as a lead brick... i have a ritchey WCS one-bolt carbon post and matching aluminium bars and stem on my CAAD 9. i'm quite pleased with those. when you go for the stem and bars, it will probably be a good idea to get professionally fitted while you're at it.
cranks are another spot to seriously consider upgrading--you'll drop weight obviously, but you'll get improved front shifting as well. i have a SRAM Force BB30 crank, which was an excellent upgrade from the gossamer BB30. if you've got the budget, go for for the cannondale hollogram SI.
but the drivetrain... run that into the ground without question. from there, you can decide if you want to go for dura-ace, or switch to sram or campagnolo.
personally, i would ditch the S80s unless your locale is flat as a pancake. i would have gone for a much lighter set of wheels, but it's pretty hilly around these parts, so rotational mass is a big concern of mine. if you've only got flat roads, aerodynamic performance might be a higher priority.
and of course, spend as much time as you can on here before you do anything. this forum is fantastic.