asterisk users - Feb 2005 - One extension, multiple endpoints

I have a 7960 desk phone and I'm running x-lite on my laptop.  They are 
both behind a NAT box so they would appear to * as being from the same 
IP.  I'm trying to make them ring at the same time but appear to 
everyone as one extension.  Is it possible to have them both register 
to * as the same extension or should I just configure them both as 
different extensions and have my dial plan ring them both and set 
outbound caller ID on both to be the same extension?