All your paying for with an exhaust is sound and maybe the tucked muffler ~$400 is a lot to spend IMO for that. They add no noticeable HP. Air Intake too. You want to spend the money, go for it.
As for wheels, depends on future plans. For me, I wish I had 17's because I want 37's and they are hard to come by for 16's. If you aren't going that big ever, you can stick with 15's or 16's and the rubber will be cheaper. Other than beadlocks, I'd suggest black soft 8 style or d window steelies.