Yeah, 10' doors aren't standard here. Basically the standard is this:
8'x7': Standard
9'x7': Bonus, extra foot wide
8'x8': Odd looking, popular upgrade in Toll Bros., etc. tract housing
9'x8': The common size in custom homes...$750,000+
I recommended the sizes I did because you have the space, and as we all like our garages here, that is the best use of it. Like Rich said especially for the car doors and everything. Space the doors a couple feet apart, as well as from the walk in door, and it will keep everything looking nice, symmetrical. If the doors are too small, the garage will look overwhelming. One big door just doesn't look as good. Hope this helped...