Playing Heroes of Might and Magic V on Ubisoft servers.

But will 40-56kb/s really be enough? Because when my friend and I tried to connect (he has a 46kb modem), it glitched terribly.

I just played a game with a foreigner at 40kb/s without any problems. Not a single lag. Lag can only occur due to the system itself. But in general, I did notice one lag when entering a town at the beginning of a turn; there's a terrible loading time, but not always. If it runs smoothly in Single Player, it will also run smoothly at 40,000kb/s online. For example, when I was playing, I was also browsing our forum.