256kbps,
It should handle 16 players fine, heck the Bash Server with 16 players never went above 24kb/sec when i was monitoring it. (and 256kbps = 30kb or so)

but with the jj2 net code being as poor as it is, and with pings and such, u can still expect Connection Time out errors and such in any large game with say 12 or more players.