Wheel width is also a determining factor in the actual distance of the outside lip of the wheel from the car, but to answer your question in a simple manner -- YES, you want to go with a smaller offset number to space the wheel out from the car and accomodate wider wheels/tires.
Jonathan
...runs 15x8s at 26mm on his first-gen cars (stock offset 40mm)
Jonathan
...runs 15x8s at 26mm on his first-gen cars (stock offset 40mm)