You just answered your own question right there. Go the "bolt on" route, it's the logical choice, as you will be able to take them off right away when the time comes.
A cam might be undesirable (to some) when it comes to re-sell time.
$800 will buy you a nice set of Stainless Power headers
with cats, if you choose the right vendor on here that is. If you want spare change left in your pocket out of a headers purchase, then TSP headers with cats it is. If you want to spend over $1000 for headers and cats, just for the "name" and warm fuzzy feeling it gives to some, then you will have to save up a bit longer then.
No cats with the headers, and off road pipes, you just about might be able to squeeze in a CAI purchase
, again if you shop around carefully and negotiate a "package deal".
Competition is fierce, the economy is tightening up, shop around.