Does anyone have suggestions/recommendations on what modems to look
The best brands are Zoom, USR and diamond supra. Make sure that they are 56k.
What's the maximum speed the serial port can handle? I read somewhere that a 56k modem is too fast.
Unless your CPU is really slow and without fast ram, this isn't true. A serial port can handle 115200 bps easily, but you will only benefit from this in dowloading text. With binary files you will get less than 56 kbps.