What are some really good running shoes?

What are some good non-expensive running shoes? Flexible and Light…the best shoes I have for running right now are nikes and they suck as far as flexibility goes…and I notice when I run top speed I run on the Ball of my feet(the upper half, is that normal?) and my nikes wont let me do that…Thanks!

What is the ideal top speed for a sprinter running high school track?

Lets say that a person had a top speed of 20mph running. Would that be a good speed for that person if they were in high school and wanted to run the 100m dash? If not, what is the speed that they should run?