Upgrading Windows NT server

I have Windows NT 4.0 server setup as a PDC and also have a Windows NT 4.0 server setup as the BDC. I have roughly 200 users using these servers and want to migrate to Windows 2000. I not only want to migrate the software but I also would like to upgarde the server hardware as well. I’m not sure where to start do I upgrade the current servers with 2000 then replace these server with new boxes or should I bring in the new servers on 2000 as bdc and then promote the to the pdc????? Can I keepthe same Domain name??? thanks