Looking for a car, best choice?

I am looking for a car, I only have about 15k to spend, I want something that has decent room, to stretch out. Also if its used something less then 50k miles on it. It has to be efficient, hopefully around 25-30 mpg city and 30+ highway. Any Suggestions on what type of car would meet these, I was looking at the scion xb but it didn't get too great of reviews, anything else?