The best system is the cheapest one.
If you want top quality, spare no expense, the borla 2 piece header system is very nice.
A quality cat back system after that, will sound nice, and flow great.
The banks cat back sounds very nice imho.
that is over 1k dollars right there. For 3 to 5 horsepower at best.
performance wise they will do very little to give you power.
My first jeep had a header, an empty cat, and a 2.5" cat back system.
it sounded cool. It was a little lighter. It gave me some extra room under there.
Thats about all it accomplished.
it is your money, enjoy it how you like, but they are not worth the money.
the factory system is not hurting you any.
I can see adding a nice small muffler, like a flowmaster to the stock system.
it would b smaller, lighter, and sound decent. Jmho.
2005 rubicon sahara lj #592