Server migration: Tiger->Leopard and new machine

I have Tiger Server on one machine. I want Leopard Server on another machine. (and then retire the current server hardware) What's the recommended way to do this? 1. Move Tiger to the new machine, get it stable, then do an upgrade install? 2. Hang Lepoard on the current machine? 3. Do a clean install of Leopard on the new machine, then migrate user data over? If so, suggestions how best to do this? 4. Some other way I haven't thought of? Thanks in advance (as usual...) dave