What you say about speakers is very true and this is why a properly set up speaker system can image so well but it sounds like you haven't heard a pair of really good headphones. The better headphones have angled drivers that were toed in by the manufacturer to achieve a certain degree of imaging. There are also headphones that have angled pads that can be adjusted for personal preference (Abyss). Moreover, you can also buy aftermarket pads with varying degrees of toe in. In fact, there are numerous threads on Head-Fi that talk about this. No one disputes the advantages that speakers have but don't make it sound like headphones can't image at all.