MP3 audio is usually encoded at rates in the hundreds of kilobits per second (topping out at about 320 kbps). You can get pretty good audio quality at 128 kbps, and adequate voice mono quality at 64 kbps. Thus, 64 to 320 thousand bits per second per stream depending on desired quality.
2 Gbps is 2 billion bits per second. (Thus, 2000 Mbps). Even if you lost half of the available port bandwidth to link overhead, etc., you could host somewhere between three thousand and fifteen thousand simultaneous MP3 streams with that much bandwidth.