Well you didn't mention a budget. Better to start from the top than the bottom :P Rag would be the safe choice, but it sounds very very flat in terms of image depth. If that's something you can live with, then its a good bet.
Fang also considers the HE-6 to be a failure too because of all the complaints about the weight, inefficiencies, and comfort. It had way too many complaints about treble etch because it was a product the market was not ready for - a time when Fiio amps were considered decent.
Take the driver out of the housing and wrap a very very thin noodle of blutack around the driver below the screw ring. Flatten it out as much as possible then push it back in the housing. Sorry forgot to take pics of the process!