Asterisk configuration for call centre

We are looking for help configuring our Asterisk platform to be used in a call center environment. The call center will support our online accommodation booking website. Call center agents will field sales queries, customer support, and perform marketing and aftersales activites. We need to be able to demonstrate a working system to a potential client at the end of June. We will scale up the system depending on the outcome of our bid. Platform: - Asterisk 1.2.8 - Centos 4.3 - OpenPBX 2.1 - 2 analog PSTN lines (expanding to 12-24) - Sangoma A200 FXO card - System is accessible over the Internet, but is behind NAT. Status: - Asterisk is installed and has been configured to answer PSTN calls. - No other configuration has been done. Estimated Call Characteristics: - 250 - 1,000 average daily calls Detailed Requirements: - We are open to recommendations from the consultant - Single incoming local number, potential to add 1-800 number - 2 queues, sales and customer service - 2-3 internal SIP phones (Grandstream GXP-2000) - Agents are mostly external and connect to the PBX over the Internet using softphones - Agents may also sign-in to the queue using a POTS phone, and the PBX will bridge calls back to their POTS phone - Agents may also be on-site using softphones or GXP-2000s. - Address book