asterisk users - Sep 2005 - Question about Asterisk connections

Hi All:

I got questioned about QoS of VoIP, I am thinking that I can configure Asterisk
server in this way: I install FXO cards to talk to PSTN as carrier side, I
configure SIP phones for our call center agents, that means I can get good
quality from PSTN, internally connecting IP phones to Asterisk for agents,
please someone confirm me if  this arrangement could provide good quality of
voice?

Many thanks,

Tielin Xu