What would be a best hardware setup for about 1000 SIP only extensions, there shouldn’t be more than 100 concurrent calls.
there is no hard-and-fast rule, have a look at the wiki for other people experiences … voip-info.org/tiki-index.php … mensioning
http://www.agilevoice.com/f/calculator/voip.htm
On this page You will find an easy hardware calculator.