I do it twice and the easiest way was:
Install new ePO 4.6 with new name and new IP Address because if you will use same DB that mean you should have same existing version on both servers with same patch which mean you need to upgrade existing ePO 4.0 on old server before going to new server.
Install new ePO 4.6 on same time keep the old one some time to ensure every thing working fine without any probelm.
you need to check in same AV to use old polices then you can upgrade it any time
you can use new version from McAfee agent and deploy it on all machines