willhub it's not so much the computer that's the problem, it's the amount of bandwith available. If your looking at 253 computers sharing a 10/100 connection there's not that much bandwith open for each computer in a LAN enviroment, and much less when your talking a broadband connection which may go up to 7-10MB.
Also the other problem comes into play with the routers, unless your going with a high end Cisco, Nortel or similar companies your going to find the hardware inside is really only meant for connecting maybe at most 25 systems.