Which DFL to raise to

Hi,

I am adding an Additional domain controller with Windows Server STD 2008R2.
For this I need to raise my Domain Functional Level.
Currently I am in 2000 Mixed mode, and I have 2 options to raise to:

1) Windows 2000 Native
2) Windows Server 2003

So which should I select, I need to have the domain on 2008 servers, and then demote the old 2003 server, by promoting the 2008 server, and taking th FSMO of the old AD.

If I take the first option, can I still raise to further "Windows Server 2003", as this step is irreversible.

Please guide.