Do the cat backs come with everything to install it i am thinking flowmaster 80 series or american thunder series

so long as you order the right one for your car, then yes it will bolt right on.

the one from summit racing

Forget that muffler, it's a horsepower robbing piece of crap.
I gained 30 HP changing to a Magnaflow with a 355

Which one flowmaster so i should go for magnaflow

I know I sound like a broken record when I say this. But if you're not heavily modded, go with what you think sounds the best. Jumping from one system to another is not going to give you huge gains. You'd be much happier with a sound that you like.

On a stock to mildly built car, just go with what you think sounds best. People are running 10's with Flowmasters everyday, they're not going to make your car seem like you're driving with a parachute on like alot of people think.

Which you think sounds better american thunder or magnaflow

Flowmaster IMO.