The Main Differences between these are the number of sip lines available and Handsets on the DECT wireless controller.
For the basics of getting the device registered, they are just about the same in regards to what they need:
1) Credentials
2) Domain
3) CODEC Choice and Priority
The Credentials are the same as any SIP device which are Domain/Proxy, User Authetication ID and Password. These can all be found in the Strategic Voice Solutions Portal by clicking the password link under the Extension, Trunk or Single Line accounts. You will see all three pieces of information on one webpage. The User Authetication ID is the actual Extension/Trunk/Line Number. The Domain/proxy is the URL of either the company or trk domain. Something like subway1.xyz.com or trk.siptpna.com depending if it is a PBX account or SIP Trunk/Single Line account.
In the Panasonic KX unit, you login into the webpage and visti the Four main sections:
1) Networks - Typically this will be defaulted to DHCP and grap the IP address from your network and point the DNS to your Router as well. If you have a different arrangement, you can make it static.
2) CODECS - By default the KX will be set to G722, G729 and G711A as priority CODECs. This shoudl be changed to G711U as the Priorty 1 CODEC, then G711A, Then G729A. You must enter all selections and they cannot be duplicated. The important part is the G711u is first priority.
3) SIP Settings - Choose the Line you want to work on, start with Line 1.
Put the Phone Number in which can be the actual phone number for the VoIP Line. The Registrar address should be your domain URL as discussed above. The Proxy Server Address, Outbound Proxy Server field and SIP service Domain can be set to the same URL as the Registrar address.
The SIP Authetication ID would be the Extension/Trunk or Single Line Number.
The SIP authetication password would be the password.
4) Line Settings - Choose the Line you want to work on, or start with Line 1. Choose the QoS settings that match your network needs or leave default. Make the DTMF Type Outband. Payload should be 101. CODEC Settings should be as discussed above.
There are Teletphone Settings as a separate tab which allow you to map SIP Lines to Handsets and other mapping capabilities that you can customize, but for bring the unit up it is best to leave on defaults.