IMPORTANT security question + most secure router

What is the best router to buy if security is most important to me (router with best firewall?)
I will not use wireless internet
And another question
If i am using 4 LAn computers with ADSL connection and all 4 of them connects
to internet trough router(router you recommend it How can i best protect one LAn computer which is
very important for me regarding the security from other 3 LAn computers which i would not watch alot
to be clean from viruses ,Trojans etc.
Is the threat that comes from my 3 LAn computers bigger than internet threat?

most consumer grade routers will not provide much trojan / virus protection


good antivirus /with automatic updates should help in this regard


setting the other pc's up with the users NOT having ADMIN rights would be good also.


(or at least their everyday account not being admin)


the watchguard /cisco ideas all seem good.... you could also look at some .nix projects

..... be prepared for a "learning curve" / spending some time on the phone to cisco CS if your not familar w/ cisco networking gear.... well as the guy points out both of those ...I've also heard good things about the Juniper networks netscreen products

dansgardian /squid comes to mind

for my part I use M0n0wall for my routing neeeds... but it doesn't do content filtering so it may not be what your looking for.