[asterisk-users] New deployment questions

[Femi]

Hi,
I'm relatively new to Asterisk and would like to set up an Asterisk box as a
PBX for a large organization and also as a switch for a small community so I
have a few questions

Which if the various flavors of Asterisk is preferred for setting up a
100-user PBX and which is preferred for setting up a 1000-user PBX?

Will Asterisk scale to 1000 PBX users, and what type of hardware would be
required to achieve this on the X86 platform?

Will using gateways like the Quintum A and D series boxes as opposed to
plugging TDM cards directly into the Asterisk box improve the scalability of
Asterisk, and will I still have to buy G.729a licenses for Asterisk if it is
only used as a switch for SIP gateways and phones? What is a good low cost
TDM gateway?

What is the best solution for user authentication for a small 100-user setup
and also for a large 1000-user setup?

Can Asterisk be used as a switch for a 10,000-user network? What hardware,
billing and authentication systems do you recommend? 

If I want to implement SS7 signaling to another telco, what gateway solution
can I use with Asterisk?

Thanks in advance for answering my numerous questions

Femi