Hi Lisa, I have some experience in moving house with cats I have moved my 5 cats 4 times in the last 6 years, they don't like moving I have to admit but they quickly settle in to new homes.
To help Rufus settle into your aunts house it is best he has his own room to start with, somewhere he can be quiet and feel safe and away from your aunts cat to begin with.
There are lots of atticles that it would be good for you to read on this website http://www.animalbehaviorassociates....n_articles.htm
make sure you read 'Helping your cat cope with change' it is exactly what you need to know!
Rufus will NOT forget you, my cats always remember my brother who lived with them nearly 10 years ago even if he hasn't been around here for months and months when he turns up they always know who he is, you can just tell they know.
I hope it all goes well for you both.