Usable power for the street?

I'll take all the power I can and use it according. Just because you have 5 or 600 hp doesn't mean you need to drive like an idiot, I've seen plenty of low hp cars do that and get themselves into trouble. As far as fuel mileage goes if I'm in my big block car I don't worry about it other than I don't want to run out. My Plymouth gets about 3mpg on e85. and my sbf does 15 on the highway and can run mid 11s. Before I retired I would drive both cars to work, 25 to 40 miles total. You just need to decide what you want from your car and build it, for me the drive is more important than the cost of it.