Worth the price ($19/year or $49/lifetime; there's a free version, 4.26, that is still obtainable). Loads and modifies even fairly large files quickly. Wide range of file types supported + many acoustic manipulations, including a very nice noise reduction filter function. There is an expression evaluator that permits the user to create all kinds of signals + a batch mode that has saved me hours of effort. These 5 are all decent programs, but I have recommended GoldWave to novices and found that they've had no trouble using it.