[Linphone-users]simple Linux <--> Windows voice chat

[Robert W. Brewer]

Hi all,

I'm wondering if those on this list can point me in the right
direction.  I'm a techie (ie nerd) and run Linux exclusively.  
I have non-technical friends that run Windows exclusively.  
We can do text chatting with Yahoo messenger, gaim, whatever.
Sometimes it would be really nice to do voice chat as well.
As some of these people are in other countries, using the
plain old telephone system is cost prohibitive.  

So I'm looking for recommendations on the simplest way to do
that.  By simple I mean very easy for my non-technical friends
to set up on their Windows boxes, and not excruciating to
get going on my Linux box.  Here are the requirements:

must support free Linux <--> Windows voice calls
must work over 56 Kbps modem connections
only 2-party calls (one to one) need to be supported
better sound quality is a plus, I'd like to practice foreign
   language skills with one of my friends
server not needed, since I can see if my friends are 
   online via gaim, etc.
it would be nice if the Linux side can work through an 
   IP masquerade box too, but this is not an absolute.

I'm running Debian Woody with Alsa sound drivers if that has
any bearing on the discussion.  

These are the options I've heard of so far:

Linux side              Windows side             comments

Speak Freely Unix       Speak Freely Windows     can it deal with IP masq?
                                                 how easy is Windows config?

Linphone                MSN messenger?           SIP proxy can deal with
                                                 IP masq?
Vovida vocal SIP        ?                        
                      
Are there other options I've missed?  I couldn't find any of the
other free-sounding SIP phones mentioned on the Linphone homepage.
Do I need some sort of always-on server for SIP to work, or can 
we just go direct peer-to-peer?

Thanks for your time and any suggestions. 

-Rob