[asterisk-users] Will this be sufficient for 20+ concurrent calls?

[harry]

This is my first time setting up Asterisk in production and we are
buying the Digium TE121-card for use with an ISDN-30 connection. We
are considering buying a Fujitsu-Siemens Primergy TX200 S4 -
http://www.fujitsu-siemens.com/products/standard_servers/tower/primergy_tx200s4.html
- for handling the calls. Quad-Core Xeon, 2.5 GHz / 2 x 6 MB / 1333
Mhz. 2 GB RAM, 3.5" SATA II discs. I know this is a rather vague
question that can not be precisely answered, but mainly handling calls
w/ playback of local gsm-files - that is, no redirection to other
clients etc. - will it be sufficient for 20-something concurrent
calls?