The shorty headers will gain almost no power, the stock "logs" are good enough for pretty much all the bolt on's you can throw at them. The problem with headers, short or long is that many tuners don't take the time to match cam timing with scavenging and don't result in much power especially on shorties
Shorty headers will change your exhaust note a lot, but do little in the way of horsepower. Go with the pullies and CMDPs and you'll see about 15HP to the wheels and a nice acceleration improvement.
Pulleys and plates will get you way more power then Shorties will ever attempt to.
EDIT: the only time shorties come close to being worth the investment is if you get the super duper coated models which cut down the underhood temps (helping your intake more then anything). Even with that you're better off getting some middle of the road longtubes since they'll cost about the same.