One of the suggestions made in the link Javern
provided would have been one of my first suggestions...allow your cat to get accustomed to a carrier long before you need to transport him. Cute, the way that was described, but (at least for me) so true to life. It works!
I've made a 4 day move by car with one cat - if I had to do it again, I would get the largest carrier that will fit in the available space. I've since learned that used (pardon me, previously owned) carriers can be found in many places, so cost would be much less than a new purchase.
With a six hour trip, I'd probably cover the carrier for the first couple of hours, then gradually uncover when he started to become inquisitive. I think Feliway could help. I would not worry about a litter pan for the trip. I'd have some water and food inside the carrier. In the car have and use some small things he is familiar with - toys, cat bed, blanket etc.
In retrospect, the most stressful parts of my move (for my cat) were the pre and post move aspects. I would NOT expose him to the removal of items in the house/apt - I would seclude him in a small quiet area (a bathroom) until all that activity was done. I would not let him see the "empty" house. On the other end of my move I would again sequester him in a small quiet area until everything was in place, then move him to a one room where he would stay for a few days, after that allowing him to slowly explore the new surroundings. In that room put all those small familiar things you carried in the car.
Here are two things that may help, a link
and a brochure