Server 2003 Migration

[zynizen]

We've got a production server running Server 2003 SP2, We want to upgrade it to 2003 R2 Enterprise.

Not much difference, but there is more features.. what is the easiest way to transfer all the information, AD data, certificates, group policy stuff.. etc..

Would it be more beneficial to just upgrade to Windows Server 2008 on new hardware?

Thanks