Some people run subs as high as 200hz too...
As long as install is correct there shouldn't be any issues. When you get to very loud volumes a proper 3-way can help tremendously with power handling requirements. However...in a car environment, 3-way + sub is a b. Since the subs are so close, tuning and transparency are a must, but you could set up a two way + sub to make up the difference for the lack of a mid-bass.
The basic rule in 2-way is that you HAVE to sacrifice somewhere...either mid-range or bass. You can't have the best of both worlds.
