The most important piece of the equation is fit, and the frame doesn't have a whole lot to do with that if you get it close, assuming head tube angle is "normal."

A better frame can potentially be lighter and stiffer, or at least rigid in desirable areas and compliant in others. It really doesn't make much of a difference in performance though.

A good example of an inexpensive frame that would be fine to road race on would be any of the Nashbar units. So much other stuff comes into play in fast riding, that the equipment becomes a pretty small piece of the equation. Once you to a certain quality level, the improvements are very minor.