Yes, RAID 1 definitely not a backup but does give you some extra time when things go bad. My plan was to use the mirror array and if a drive went down just toss it and simply G4U the good drive to bring the array back online.
I have heard of the firewall that you mentioned. It seemed to have good reviews. I have just been using m0n0wall forever so I am a bit partial to that. Also it runs on CF here so pretty low consumption for a PC size box. I'll have to get an embedded box one of these days! Also, m0n0wall is kind to Asterisk PBX for remote phones where other firewalls have given me problems in configuration. At the end of the day I think it would be just too much configuration trying to configure NAT and proxyARP for every port and IP. I am going to just run ISPCONFIG right on the pipe in the DMZ and use the built in firewall with generic rules for all IP's. I'll run a separate server on the spare IP (probably a database server to take the load off of ISPCONFIG) where my voIP server and LAN is located.
Thank you for your input!
Any other suggestions welcome!