Tiger to Leopard migration with a twist

Firstly, apologies if I have missed any relevant posts on this forum during my searches, but I haven’t found anyone in exactly the same situation. I have a G5 Xserve running 10.4.11 as my production server. It has fallen out of warranty and will shortly be replaced by a new Intel Xserve. I also want to deploy OD and portable network homes, so I will need to migrate my 40 users to a directory structure as well. I am really hoping I can still get one with 10.5 preinstalled. Snow Leopard is a further complication I don’t need. Mainly as I wanted to use the existing Xserve as an OD replica, so I wanted the same version of OS on both the master and replica. If this isn’t going to be an issue, then please advise. I don’t currently use ACLs, only POSIX permissions. I run AFP, SMB, DHCP and DNS services I wonder if anyone has any nuggets of good advice here, any gotchas that I should look out for? Or even a blow-by-blow plan if you’re feeling really generous ☺ Thanks, Greg