Anearlier Version of X-Lite supported multiple registrations.
Of course, calls are through a headset or USB device or adaptor.
See post for download :
http://forum.voxalot.com/voxalot-gen...html#post11451
The commercial version of the X-Lite also supports multiple accounts, as does Express Talk, Ekiga (Linux), and perhaps others too.
Express Talk VoIP Softphone for Windows - SIP Service Providers
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