Asterisk PBX Call Forwarding/Lead Tracking System

We are looking for an experienced VOIP person to help us set up an advanced phone system. Basically, when someone calls our toll-free number we want them to receive a prompt that says, "Thank you for calling _, please enter your extension now." Once they have entered an extension, they call will be forwarded to our clients (on a different number, not associated with our phone server). When that client answers the phone, I want them to hear "Another lead from _" and a chime. Then it should connect the call. I will need the system to be able to handle well over 1,000 different extensions (EXTENSION 2113), as each one of my clients will require a different one. Finally, I need the system to be able to log the number of calls received at each extension in our MySQL database (so we can see the total number of leads that have been generated through that number) and then send a recording of the call to an email address associated with that extension. We haven't decided whether or not to have our own Asterisk server running in the office -- or if we should just co-locate with a host online. We've also been told that Gafachi is a great provide, but your input here would be greatly appreciated.