Firewall for WAN or Intranet

We currently have a Sonicwall soho3 for our firewall. They want to have a webserver on a dmz. What firewall should i suggest for either the WAN or intranet. I could use the sonciwall for the intranet firewall and purchase a WAN firewall. Budget is $400.00 or less. No need to VPN solution or content filtering as we already have them in place. Should i get another Sonicwall? I might be able to get an older PIX 501. But i have concerns as it is very old.

Thanks for your input.
Kevin