For all cars but yours, the answer is yes.
For yours, the answer is maybe. The 318s had came with the base stereo (6 speakers). Almost all 325s had the "premium" stereo (not HK). This upped the speakers to 10. While there are 318s with an amp and 10 speakers, they are rare. The easiest way to tell is by looking at the door. If you see two speakers by your knee, then its amped. One, and its not.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>