ADSL router for a medium size network. any recomendations please?

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Hi

We have a network with about 200 computers, but normaly only about 50 will be connectod to internet at the same time. We have a cheap ADSL router (a tipical personal router) which hangs several times a day when there are many connections. We are thinking on changing the router and we are thinking on some routers like the following:

Cisco 857 Integrated Services Router puertos

there are others like the following but they are fom"home users" or "small offices" and i think they may have troubles too with many connections

NETGEAR RangeMax Next Wireless ADSL2+ Modem Router DG834N

Router Linksys WAG325N ADSL2+ Gateway - Wireless-N (802.11N)

we need ADSL2+, NAT, ethernet 100, we dont need wifi.

any recommendations?

thanks