The ANT-3x3-2005 and ANT-3x3-5005 each come with three antennas, that will give you six omni antennas to connect to the AP-274 that has 6 connectors. So
1xAP-274
1xANT-3x3-2005
1xANT-3x3-5005
6 antennas total in this setup
Am curious though, why not get the AP-275 if these are the antennas you will be using?