It's really more of a connection problem you have to deal with. Many people on a cable connection = bad. I would say anything over 1 gighz and 512 would do quite well for a dedicated server. (My old server ran on a 700ish mhz p3 with 512 ram on a cable modem, got about 10 - 15 people on average and had - no - lag.)
__________________
:O
|