It might not seem like a huge upgrade but I could live with the HD650 as my only headphone. Can't really say that about any other headphone in stock form. They also scale very well. About the only things that scale better are HD800 and Utopia.
People use HD650 with $7000 amps and $5000 DACs like the Eddie Current Studio and Metrum Pavanne.
People use HD650 with $7000 amps and $5000 DACs like the Eddie Current Studio and Metrum Pavanne.