suggestion for firewall equipment and layout!

[jimmyjiang]

hi,

recently I have to design and implement a new media size company network(50+ users) , all the workstation is windows 2000 or xp pro, can anybody have experience in this field can give me any suggestion of the whole company network layout,and what kind firewall equipments and antivirus softeware is fit for a media size comany, and if my boss prefer linux and free bsd as firewall, what version is the best and installion and configuration informaion.

thanks!