Multiple cats can be moved in the car with some forethought.
I have moved 5 cats from NH to AZ. We got a great dane crate for free. We took a leftover piece of wallboard/paneling (thinner than plywood) and cut it to the outline of the center of the crate, where the top and bottom separate. We drilled holes where the bolts and wingnuts go through, and cut out a space in front for the kitties to jump through at the door. We reassembled the crate with the paneling in the middle so they had two floors. On the bottom we used a tiny travel litter box from WalMart, although you could just use gift boxes or cut out cereal boxes. The litter box needed changing so often I might just do that next time and just throw it out.
We took out the middle seat of the minivan and put that in the trailer with the stuff, so we had room for the carrier in the van. They had enough room to move around and get some space if anybody was having a cranky moment. We do have one who doesn't get along with anybody else, she did settle after a little while and just staked out a corner that was hers. We have another one who yowls the entire time she is in the car, she did eventually stop. I think they liked it better being together, they were comforted by that much normalcy. We did find a few hotels along the way that took pets (warning them that we had a lot of pets just in case) so they got some out time.
This spring we are moving from SD to NH with 6 cats. This time we have a cargo van and are going to use one of those 4 level ferret palaces for the cats, but most vans would be too short for this.