The Sticky "What's on Nimiq 3" explains what channels you are not receiving from the 91 slot.
Be aware that Expressvu is having significant rainfade issues on Canada's west coast with Nimiq 2.
They will be addressing these problems starting December as they will be putting an old DirecTV satellite into service colocated @82. DTV satellites do not have as great a beamwidth as Nimiq1/2 do.
What exactly Expressvu will do shuffling HD channels is unknown at this time. However, one cannot expect a signal from N4 in areas not receiving N3 signal now.
If I was in your location, I would be taking a wait and see approach before spending $$ on Expressvu.