Selle Italia saddles for me.
I'm currently using the SLR Flow (Flow means it has the cutout) and it's super comfortable for long rides. It is an easy saddle to move around on also.
But if the SLR is too easy to move around on I would recommend the good ol' Selle Italia Flite. It has just a bit more of a curve to it allowing you to find that "pocket" to settle into while still giving you freedom to move around if needed.
Yes, cycling shorts with a chamois is a necessity. Personally I really only ride in bib shorts (or tights when its cooler) for total comfort.