Actually, I prefer not to hear that gibberish of the modem connecting. Turning off the sound is one of the first things I did in Mac OS X. You should feel blessed that you don't hear anything as long as it works. I did have some problems getting Mac OS X to recognize my modem. A call to Apple straightened that out - select a different modem. Why which one? Call Apple to see which modems were put into which machines.
Incidentally, my brother is running Mac OS X 10.0.4 on his 266MHz iMac with 64MB RAM. It's slow as hell, but it works. Oh, almost forgot, it pages out right at startup. Crunch crunch crunch...