Another thing to watch for are if you're going to true dual headers, some manufacturers (Ex. Rinehart) have slightly larger headpipes that won't allow you to use standard 1-3/4" factory sized slip-ons. Their slip-ons come in two sizes, one for stock pies and another size for their true dual headers. Ask questions before you buy.V&H headers are a good choice but can get pricey.
Fullsac also makes a conversion kit for about $180 that utilizes most of your stock pipes and heatshields and I run a set of them. Helped with the heat on the right side of the bike. No loss in torque as others have claimed ridiculously that I could tell. I'm happy with their kit and it was worth the investment. B&E also makes pretty much the same kit and they've gotten great reviews on their modified mufflers...they take stock slip-ons, rework them and guys that have bought them have nothing but positive things to say about them....not too loud with a good low tone, perform well, look stock and are very reasonably priced at about $150 or less for a pair.
A fueler is a good idea if you plan on running a free flow air filter and a less restrictive slip on like others have mentioned. I chose to go with a Dobeck TFI GEN 3 unit and I love it.......first unit gave me some issues but they stand behind their products and warranteed it immediately. I was still able to ride while it was being reshipped, although the bike ran very lean. Do a little research as to how much you're willing to spend and go from there. You have several options from affordable to expensive.