I have 18 x 10 rears with et 47mm. You will need to tie back the e-brake cable, but they do fit without rubbing the strut (my car is lowered about 1.5" from stock).
You should be fine with et 46, subject to your tire choice; fronts will be fine, as well.
The negative offset of 46mm from centerline brings the wheel closer to the inside; i.e. greater the negative value, the further in toward the strut. Conversely, anything less than et 46 will push the wheel out toward the fenders, causing another set of problems.
Here is a simple offset calculator that may help you understand the process:
http://www.1010tires.com/WheelOffsetCalculator.asp