Front door speakers

[Skyline]

I need to replace the at least one front door speaker in my daughter's X5. Anyone know the cost of the factory unit?

Are the factory speakers decent, or can I gain a noticible improvement by upgrading to some better quality speakers?

In my current DD, I used MB Quarts all around, which I was extremely happy with, but those are VERY costly, so I'm open to other suggestions. And from the size of the speaker grill, it looks like these are a bit smaller. Are these 5"??? I don't think I want components either; just replacement drivers.