factory subwoofer?

Did all the XLS' come with a subwoofer? Mine has a 8" factory installed speaker. It sounds pretty good for such a small sub. I wonder if I was to replace it with a top name sub would it sound better or really no change?

Not all of the XLS's came with the subwoofer. The system is a Harmon application.

Although my car did not come with the sub, I upgraded all of the door speakers, and added a Bazooka subwoofer to the system...quite an improvement!