I have more than 1 gpo in the same OU. (server's OU),No, no. Just place it in Merge mode when you enable the loopback processing. It applies all you settings from the first GPO and then overwrite the proxy settings from the second one.
Andrew, I have always done it this way and it works like a charm. For GPO's
applied to Servers, for every group policy that contains User settings, you
need to enable loopback processing. If your way works, then that's news to