I am new to Cisco VoIP and I'm wondering how best (cheapest way) to
configure a Cisco system for VoIP.

Specifically, I need to be able to terminate 8 simultaneous calls over
4 ISDN BRI interfaces.

I have seen references to a VIC-2BRI card and an NM-4B card in the
literature. Obviously, for economic reasons, the 4B card seems
preferable, however I do not understand if it has DSPs capable of
handling the VoIP Codecs. (I need to run G.723.1)

Is it possible to run G.723.1 voice over the ISDN interfaces on an
NM-4B-U card?

Next question, how would I configure a system to run voice over 3 ISDN
lines and data (WAN) connection over the last one?

What is the minimum recommended router chassis to handle this config?

Thanks for any assistance with this.

Kant