Switching FreeBSD machines

[RL]

Hi. I have FBSD 5.3 on one machine. I'm thinking of buying a Dell
420SC Server and would want to use FreeBSD on that. I went through a
hard time getting things to work on my current machine such as Java
and maybe a few other things, so I really would rather not start from
scratch. And I don't want to swap hard-drives because the Dell comes
with a nice Serial ATA drive I want to use. My only option might be to
clone the old FBSD box using g4Unix and putting it on the Dell. Would
kind of problems and headaches would I have with that?

Edit: Current machine is an Athlon and Dell server is a P4.