[Asterisk-Users] SER or not to SER?

[Nahuel Alejandro Ramos]

Hi everyone,
  I have some doubt about use or not to use SER.
  I need a solution using a single linux box that manages, aproximatly
500-1000 registred SIP users, but not more than 50 simultaneouly
calls. My plan is to use between 3 to 5 Cisco 26xx PSTN gateway in
diferents cities of my country (Argentine) connected through Internet
(with public IP).
  I was searching for SER solutions (and works perfectly) but it does
not support Prepaid Billing. So I post a message (on SerUsers
maillist) and everybody said me to use Asterisk to use a Prepaid
Billing App., so I install Asterisk.
  I "googled", read this maillist (and post some message) and I
receive some helpful answers recomending me to install ASTCC, so I
install it too and work perfectly too.
  My questions (if someone could help me) are :
   1) What platform (hardware) do I need to support my call flow
(500-1000 registers and 50 simultaneouly calls)?
   2) Do I need to install SER?
   3) If YES, do I need to register my SIP clients on SER and forward
all the calls to Asterisk?
   3) If NO, do I need to register my SIP clients on Asterisk and
forward all the calls to SER?
   4) Can I use only Asterisk to REGISTER, AUTH, ACC, ROUTE CALLS,
etc, SIP clients?
   5) Could I use extension.conf file to route my calls to my
diferents Cisco PSTN GW?
   6) And how can I use MySQL instead of file? (I have created the DB
and tables but I do not know how to make Asterisk use it instead the
extension.conf file)
   7) I found easy to use only Asterisk, but I have read that it uses
to much CPU and memory, is that true?
   8) Could anyone some me information about how to configure Asterisk
to receive calls through Cisco PSTN GW?
   9) THANK YOU VERY VERY MUCH!!!

           Nahuel Ramos.