Server Configuration Advice

I am having some second thoughts on a configuration I had planned earlier. I would like someone to tell me if what I am thinking of doing is going to work.

Currently, I have 3 Macs running OS X Server.

Server A: (Dual 1GHz Power Mac G4, 1.5 GB RAM, Mirrored drives)
OpenDirectory Master, DNS, DHCP, Windows PDC
Total users in LDAP directory: 1200 users

Server B: (933MHz Power Mac G4, 1.5 GB RAM, Mirrored drives)
Connected to Server A directory system, AFP, Windows, MacManager
Teacher’s Home Directories are this server’s primary role
Theoretical maximum connected computers: 125
(This is if all of the teacher’s and staff users have logged in simultaneously to a computer)

Server C: (933MHz Power Mac G4, 1.5 GB RAM, Mirrored drives)
Connected to Server A directory system, AFP, Windows
Students’ Home Directories are this server’s primary role
Theoretical maximum connected computers: 165
(This is if all of the student’s computers have students logged in simultaneously)

Now, I purchased two brand new Xserve G5s. Budget was an issue. I would have like to have purchased three Xserves to replace the 3 Power Mac G4s, each with three drives in a hardware RAID, and each with dual processors. Instead I was limited to about $7,000. As you know, that doesn’t buy you much. So both Xserve G5s are spec’d with two drives, 1GB RAM, and a video card.

In addition to the amount of users I have now on my directory master, I am going to add approximately another 1,600 for authentication purposes. These two new Xserves would move the other two servers down the line for use in another school.

Do you think that if I combine one of the server’s roles (serving home directories) with the LDAP master, DNS, DHCP, and Windows PDC onto one of the Xserve G5s that it’s going to make life miserable? Basically what I am asking is will it work reasonably well if I consolidate my three server setup into the 2 new Xserves?

Also can I change the subnet mask on OS X Server after its setup without it freaking out or is that a no-no? I know changing IP address is a royal pain the arse.

I am entertaining suggestions, because I know somebody here has the answer!