URGENT: WSUS on DC or Storage server or SBS 2000

We have a Windows 2003 network. I have 3 servers: Domain Controller (DHCP,DNS,Exchange, Remote VPN server,Application server), Storage Server (File server, Print server) and SBS 2000 which we primarily run as SQL Server. I would like to implement WSUS.

Which server is the better choice and why?

Are there any known issues with using WSUS on a DC? I read somewhere that you should not run DHCP and WSUS on the same server (some security issues). I am leaning towards the Storage server but then I have to install IIS on the server which already exists in DC.

Can someone help (URGENT)

Thanks in advance

Regards,