Reverse Squid proxy on a DMZ

Is this a good idea? The plan is to have the reverse squid proxy on the DMZ and it will be directed towards a web server on a separate subnet. Then, the LAN will be on another subnet. What are some opinions on this setup?

I will be running either IPCop or Smoothwall on the Linux box. Also, any suggestions on solid linux pre-built pcs? I’ve looked at some from store.madtux.org and they seem solid. Any experience with these?