Will each visitor load only 1 page each? How big is that page on average?
Suppose all visitors come evenly distributed between 08:00 and 16:00 (8 hours), you then have 125 visits per hour, or 0.035 visitors per second.
0.035 visitors per second sharing 56 Kbps, gives 1600 Kbit per user, which translates to approx 200 KByte per page, including pictures and videos.
I'd say it depends very much on your content and user behaviour if the upstream bandwidth will be enough. The visitors will probably think your site is slow if you have many visitors at the same time, or if your pages are large.