Hi and welcome to AF
Well listen dude there are no dumb questions so dont worry about it, anything you have questions on just ask
Well first off I suggest getting a cat-back system. This will improve exhuast flow, and help expel and keep exhuast gases from going back into the combustion chambers, which takes up space, thus having less volume for the air/fuel ratio to fill.
Get a cat-back system if you're really looking for performance.
The mufflers you see for $100 wont do anything man. They're just for sound, and if thats what you want then get that. They're just there to 'look' pretty, but most of those mufflers are all sound, and the sound you get is usually that high-pitched weedwacker kinda sound, that sounds like your car is gonna explode :hehe:
Oh and the Axle-backs are just replacements from the rear axle back into the muffler.
So the decision is up to you and what you wanna do with your car.
$100 for just sound
or
$400 for something that will actually improve throttle response etc...
Anymore questions you have there are LOTS more knowledgeable people in here that can answer them!

Good luck with the car!