The short answer is yes, more expensive AV receivers sound better. The longer answer is that more expensive AV receivers will generally have better components and build quality, providing outstanding sound quality. However, you will also need high-quality speakers, source material, and proper installation with good quality interconnects to get the full benefit. Plus, you should place it in a room that allows you to hear the improvement in sound. 'Better sound' is a very subjective thing. For some people, it will sound better if you just add extra bass. You don't need an expensive receiver if you want that; just turn up your subwoofer! Audiophiles need a more balanced sound, and a costly receiver will provide high-end detail, a balanced mid-range and controlled bass.