I got my HD600's and I am very pleased with them. Excellent build quality and they sound fantastic, very comfy too.
Now, my 10 year old sound card (Creative Fatality Titanium Pro) provides decent power but having to move them constantly between my sound card and my audio gear is a bit tedious, my mixer doesn't seem to provide enough juice. So I'm thinking that I could get an audio interface, which not only would provide better amplification, but would allow me to switch between headphones/monitors very easily. I'm thinking something like the Focusrite Scarlett 6i6. Do you think that it would drive my 600's well enough? I suppose it could be quite the improvement over my Creative card, right? Is it possible for such an audio interface to replace a dedicated amp?