It would help to know what you are after here. Sound? Performance? Long life of the parts?
Your Gen 1 is at least 20 years old, and the money you would spend on exhaust system "improvements" might better be put into components that truely improve the reliability of the drivetrain or suspension components - just saying.
Performance upgrades on the 2.5i NA are going to get minimal returns.
And I'm not saying to upgrade anything - I'm just suggesting that a 20+ year old Gen 1 may best benefit from regular maintenance and replacement of the drivetrain or suspension components that require it, if you want to keep it around a while longer.