My old custom made tube amp is being repaired and I need a portable amp anyways. I'm not a huge fan of the tube sound, I much prefer technical accuracy(reason for the HD800's) as I use my cans to keep my ears trained. A friend loaned me his Ibasso D10. I have not played with the opamps yet but I found the highs too laid back and stage narrow. I would prefer a DAC/AMP since I use it with my laptop mostly and Ipod less often.
in Short. Non colored amp, great open staging. Portable and can get the 300ohm cans pretty motivated as I like it loud.
Budget, preferably under $350.