[Serusers] Advice needed

[Michael Ulitskiy]

Hello,

I'd like ask for advice on what is in your opinion the best solution 
in the following scenario.
I have a bunch of sip servers (asterisk boxes as my users need pbx
functionality) that can make sip call to each other and my PSTN 
gateway. Now I want to purchase PSTN terminitaion in several
different markets (and probably more in the future). All those
terminations will require authentication.
I want all my boxes when they see non-local call to send it to a
central routing server that would determine where this call should
be sent and authenticate to the appropriate provider so that I don't
have to configure all credentials on all asterisk boxes. Also I want
it not to deal with the media at all. All media streams should go directly
from asterisk box to the PSTN termination provider. 
So basically it should be central SIP router that is able to authenticate
calls if neccessary.
I thought I could do it with SER and its UAC module, but it appears
UAC module doesn't work and probably won't work (see my previous
post in this list about UAC backport to 0.9.0).
Also I don't want to use asterisk in this place as asterisk always wants to
stay in media path and I'd really like to avoid of getting into hassle with
re-invites.
So the question is what are my options and what you would advice
as a solution. Are there any software out there that can do it (preferably
open-source, of course) or what else you could suggest to do to get
desired results.
Thanks a lot,
-- 
See you later,
                    Michael