PMB...We are talking about factory speakers here!
Whether or not you can buy better aftermarket speakers is another story.
The fact of the matter is Harmon Kardon owns Infinity, thats why they install HK speakers in BMW, Mercedes, Audis etc and install Infinity speakers in GM, Chrysler, and Ford.
The factory HK speakers are top of the line, the deck is the weak spot!
Many people think its the other way around, this cannot be further from the truth.
Start with a great head unit and build from there!
I have a 318i as well and changed out the factory deck and didnt touch the speakers, it was like I install 4 new top of the line speakers.
I can tell the HK speakers are top of the line, the deck has to be replaced to clean them up!
I also spoke to a stereo installer who told me the HK speakers are top grade and tells anyone who wants to change them out to spend they're money on the deck!
Only problem is when you change the deck it becomes a target!
I don't want anyone breaking into my car to get the stereo