[help] Question about Tapi and Asterisk


I have read that Tapi has two architecture: one is the first-party-soulution and the other is the third-party-soulution.
For a office with 25 phones I think the third-party-solution is better. So I need a server , which actually makes the calls.
My question is: is that possible that I spare the NT -server and use *box to take his job?and how , if it is possible.