Thanks for looking over my configuration - I'll have to test these changes, enable the other codecs and see what happens.

Right now I have the S675 in the router's DMZ and SPI firewall functions turned off, but once I settle on a good, working configuration, I'll take it back out of the DMZ and forward ports to it, if needed.

It might be the router, I'm using an older Linksys WRT54G running DD-WRT and might not be voip friendly.