Speakers normally aren't my fancy, and since the speakers in my SLS are Bose, I was hoping to get a second opinion from the people here about my problem.

The front left speaker, just left of the steering wheel, is blown. Not too noticeable, just crackles every now and then on a few songs.
So, i asked a buddy of mine who runs a car detailing service about it, he started telling me about "tweeters" and things that intertwined the left door, left, middle, right, and right door speakers all together, so if i were to replace one, i would need to replace them all. i don't have that kind of money, and i was wondering if he's trying to rip me off by telling me to do that. what should i do?