[2005 6mt]

Depends what trim package. The touring has a factory sub and sounds pretty good, It can handle being pretty loud without distortion

This. The Touring is noticeably better than the other trims. It's really not bad IMO, and I came from a semi-decent Alpine Type-S system w a 10" infinity sub I had built in my 8th gen coupe.
Some aftermarket replacement speakers with a high sensitivity would go a long way I believe.