I dont recommend a dual exit kit on a smaller displacement engine. You might end up losing your low end torque from the lack of back pressure. You would be better off with a single exit kit for a true power increase.
You could possibly go dual by either having the over axle pipe split into a Y with a smaller diameter tubing - I would not go above 2 1/4" tubing. Or you could use a singe in dual outlet muffler - again dont go above 2 1/4" tubing otherwise your bottom end power could suffer
You are probably going to find most aftermarket companies only offer a single exit kit.
I got the gibson sigle tip cat back exhaust and it sounds good and could tell there is a power gain and with my k&n i had a good mpg gain. with the gibson exhaust it sounds beefy but isnt annoying driving on the hiway
I'm always for going to a shop and have it all done. It usually ends up cheaper than going with a kit. I got my muffs(multiple...i've had alot of muffs on my truck), and had it hung for $150. That's just single out.