Eryler I was use only sangoma quad without hardware echocancelation and on the same machine was working fine with 120 councurent calls.
# Autogenerated by /usr/sbin/dahdi_genconf on Mon Sep 6 14:33:24 2010
# If you edit this file and execute /usr/sbin/dahdi_genconf again,
# your manual changes will be LOST.
# Dahdi Configuration File
# This file is parsed by the Dahdi Configurator, dahdi_cfg
# Span 1: TE4/0/1 "T4XXP (PCI) Card 0 Span 1" (MASTER) HDB3/CCS/CRC4
# termtype: te
root@asterisk7:/var/local# cat /etc/asterisk/chan_dahdi.conf
;autogenerated by /usr/sbin/wancfg_dahdi do not hand edit
;autogenrated on 2010-02-04
;Dahdi Channels Configurations
;For detailed Dahdi options, view /etc/asterisk/chan_dahdi.conf.bak